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Groton Weather Records (USC00063207)

Record envelope, standing records and threshold days for Groton (USC00063207), Connecticut, United States, with 77 years of record.

Key Facts for Groton

  • Groton (USC00063207) is a weather station in Connecticut, United States at 41.35 latitude and -72.04 longitude, 12 m (40 ft) above sea level.
  • The station reports from 1948 to 2024, 77 years of record.
  • 1,464 records set at Groton still stand.
  • Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
  • Groton set a daily record high minimum temperature of 8.9 C (48.0 F) on 30 December 2024.

About the Station

  • Location: Connecticut, United States, 41.35 latitude, -72.04 longitude.
  • Elevation: 12 m (40 ft).
  • Period of record: 1948 to 2024, 77 years.
  • Eligible elements: tmax, tmin, prcp, snow, snwd.

Daily Record Envelope and 2026

0 days at or beyond a record
Daily record high and record low at Groton, with 2026 drawn through them The band shows the record high and record low for each calendar day at Groton. The lines show the 2026 daily maximum and minimum. 0 days in 2026 matched or passed a record. Temperatures are in degrees Celsius. -40-2002040 JanFebMarAprMayJunJulAugSepOctNovDec
The band shows the record high and record low for each calendar day at Groton. The lines show the 2026 daily maximum and minimum. 0 days in 2026 matched or passed a record. Temperatures are in degrees Celsius.
Daily record high and record low at Groton, with 2026 drawn through them
MonthHighest record highLowest record low2026 highest maximum2026 lowest minimum
Jan20.6 C (69.1 F)-25.6 C (-14.1 F)n/an/a
Feb21.1 C (70.0 F)-24.4 C (-11.9 F)n/an/a
Mar25.6 C (78.1 F)-17.8 C (0.0 F)n/an/a
Apr31.1 C (88.0 F)-10.0 C (14.0 F)n/an/a
May32.8 C (91.0 F)-1.1 C (30.0 F)n/an/a
Jun35.0 C (95.0 F)3.3 C (37.9 F)n/an/a
Jul38.3 C (100.9 F)8.3 C (46.9 F)n/an/a
Aug37.2 C (99.0 F)5.0 C (41.0 F)n/an/a
Sep33.9 C (93.0 F)-1.7 C (28.9 F)n/an/a
Oct30.6 C (87.1 F)-5.6 C (21.9 F)n/an/a
Nov26.1 C (79.0 F)-13.3 C (8.1 F)n/an/a
Dec20.6 C (69.1 F)-23.3 C (-9.9 F)n/an/a

Which Years Hold Standing Records

1,464 standing records
Standing records at Groton by the year they were set 1,464 records at Groton still stand. 1962 holds the most, with 38. 0102030401957: 241958: 321959: 311960: 231961: 331962: 381963: 381964: 321965: 271966: 211967: 351968: 211969: 151970: 181971: 151972: 241973: 171974: 281975: 241976: 351977: 241978: 231979: 341980: 171981: 231982: 211983: 151984: 241985: 231986: 241987: 191988: 231989: 201990: 331991: 331992: 201993: 211994: 141995: 271996: 231997: 111998: 171999: 92000: 252001: 222002: 342003: 142004: 92005: 12007: 172008: 182009: 112010: 332011: 212012: 222013: 42014: 82015: 352016: 222017: 342018: 252019: 62020: 202021: 172023: 172024: 201957196419711978198519921999200720142021
1,464 records at Groton still stand. 1962 holds the most, with 38.
Standing records at Groton by the year they were set
Year setStanding records
195724
195832
195931
196023
196133
196238
196338
196432
196527
196621
196735
196821
196915
197018
197115
197224
197317
197428
197524
197635
197724
197823
197934
198017
198123
198221
198315
198424
198523
198624
198719
198823
198920
199033
199133
199220
199321
199414
199527
199623
199711
199817
19999
200025
200122
200234
200314
20049
20051
200717
200818
200911
201033
201121
201222
20134
20148
201535
201622
201734
201825
20196
202020
202117
202317
202420

All-Time Record Progression

5 new records
When Groton set new all-time records 5 all-time records were set at Groton between 20 January 1987 and 27 January 2015. Each dot is a new record. Record snow depthRecord high maximum temperatureRecord high minimum temperatureRecord daily snowfall20 January 1987: Record snow depth 61.0 cm (24.0 in)21 July 1991: Record high maximum temperature 38.3 C (100.9 F)25 July 2001: Record high minimum temperature 25.6 C (78.1 F)27 January 2015: Record daily snowfall 61.0 cm (24.0 in)27 January 2015: Record snow depth 66.0 cm (26.0 in)199019952000200520102015
5 all-time records were set at Groton between 20 January 1987 and 27 January 2015. Each dot is a new record.
When Groton set new all-time records
DateKindDetail
1987-01-20Record snow depthRecord snow depth 61.0 cm (24.0 in)
1991-07-21Record high maximum temperatureRecord high maximum temperature 38.3 C (100.9 F)
2001-07-25Record high minimum temperatureRecord high minimum temperature 25.6 C (78.1 F)
2015-01-27Record daily snowfallRecord daily snowfall 61.0 cm (24.0 in)
2015-01-27Record snow depthRecord snow depth 66.0 cm (26.0 in)

Wettest Day of Each Month

Sep: 188.7 mm (7.4 in)
Record daily precipitation for each month at Groton The wettest day on record for each calendar month at Groton. The most was 188.7 mm (7.4 in) on 21 September 1961. 050100150200 Jan: 72.6 mm (2.9 in), 6 January 1962 Jan Feb: 72.6 mm (2.9 in), 13 February 2008 Feb Mar: 80.0 mm (3.1 in), 26 March 1988 Mar Apr: 83.6 mm (3.3 in), 13 April 2004 Apr May: 89.2 mm (3.5 in), 25 May 1967 May Jun: 160.0 mm (6.3 in), 5 June 1982 Jun Jul: 111.3 mm (4.4 in), 1 July 2009 Jul Aug: 130.6 mm (5.1 in), 12 August 1955 Aug Sep: 188.7 mm (7.4 in), 21 September 1961 Sep Oct: 122.4 mm (4.8 in), 5 October 1962 Oct Nov: 86.1 mm (3.4 in), 5 November 1985 Nov Dec: 93.5 mm (3.7 in), 3 December 1986 Dec
The wettest day on record for each calendar month at Groton. The most was 188.7 mm (7.4 in) on 21 September 1961.
Record daily precipitation for each month at Groton
MonthRecord daily precipitation (mm)Date
Jan72.6 mm (2.9 in)6 January 1962
Feb72.6 mm (2.9 in)13 February 2008
Mar80.0 mm (3.1 in)26 March 1988
Apr83.6 mm (3.3 in)13 April 2004
May89.2 mm (3.5 in)25 May 1967
Jun160.0 mm (6.3 in)5 June 1982
Jul111.3 mm (4.4 in)1 July 2009
Aug130.6 mm (5.1 in)12 August 1955
Sep188.7 mm (7.4 in)21 September 1961
Oct122.4 mm (4.8 in)5 October 1962
Nov86.1 mm (3.4 in)5 November 1985
Dec93.5 mm (3.7 in)3 December 1986

Period of Record Coverage

1957 to 2024
Days with data per year at Groton 66 years of record at Groton, 1957 to 2024. 14 years have data for under 90 percent of days and are left out of rankings: 1957, 1988, 1989, 2005, 2007, 2009, 2010, 2012 and others. 1957: 250 of 365 days1958: 365 of 365 days1959: 365 of 365 days1960: 364 of 366 days1961: 365 of 365 days1962: 364 of 365 days1963: 365 of 365 days1964: 366 of 366 days1965: 365 of 365 days1966: 365 of 365 days1967: 365 of 365 days1968: 366 of 366 days1969: 365 of 365 days1970: 365 of 365 days1971: 365 of 365 days1972: 366 of 366 days1973: 363 of 365 days1974: 365 of 365 days1975: 365 of 365 days1976: 366 of 366 days1977: 365 of 365 days1978: 364 of 365 days1979: 365 of 365 days1980: 364 of 366 days1981: 361 of 365 days1982: 335 of 365 days1983: 361 of 365 days1984: 356 of 366 days1985: 345 of 365 days1986: 353 of 365 days1987: 363 of 365 days1988: 298 of 366 days1989: 311 of 365 days1990: 359 of 365 days1991: 365 of 365 days1992: 334 of 366 days1993: 365 of 365 days1994: 365 of 365 days1995: 364 of 365 days1996: 364 of 366 days1997: 364 of 365 days1998: 332 of 365 days1999: 364 of 365 days2000: 361 of 366 days2001: 330 of 365 days2002: 359 of 365 days2003: 363 of 365 days2004: 354 of 366 days2005: 58 of 365 days2007: 321 of 365 days2008: 352 of 366 days2009: 268 of 365 days2010: 296 of 365 days2011: 358 of 365 days2012: 207 of 366 days2013: 184 of 365 days2014: 273 of 365 days2015: 332 of 365 days2016: 274 of 366 days2017: 333 of 365 days2018: 273 of 365 days2019: 212 of 365 days2020: 335 of 366 days2021: 181 of 365 days2023: 333 of 365 days2024: 365 of 366 days1960197019801990200020102020
66 years of record at Groton, 1957 to 2024. 14 years have data for under 90 percent of days and are left out of rankings: 1957, 1988, 1989, 2005, 2007, 2009, 2010, 2012 and others.
Days with data per year at Groton
YearDays with dataShare of yearComplete
195725068%No
1958365100%Yes
1959365100%Yes
196036499%Yes
1961365100%Yes
1962364100%Yes
1963365100%Yes
1964366100%Yes
1965365100%Yes
1966365100%Yes
1967365100%Yes
1968366100%Yes
1969365100%Yes
1970365100%Yes
1971365100%Yes
1972366100%Yes
197336399%Yes
1974365100%Yes
1975365100%Yes
1976366100%Yes
1977365100%Yes
1978364100%Yes
1979365100%Yes
198036499%Yes
198136199%Yes
198233592%Yes
198336199%Yes
198435697%Yes
198534595%Yes
198635397%Yes
198736399%Yes
198829881%No
198931185%No
199035998%Yes
1991365100%Yes
199233491%Yes
1993365100%Yes
1994365100%Yes
1995364100%Yes
199636499%Yes
1997364100%Yes
199833291%Yes
1999364100%Yes
200036199%Yes
200133090%Yes
200235998%Yes
200336399%Yes
200435497%Yes
20055816%No
200732188%No
200835296%Yes
200926873%No
201029681%No
201135898%Yes
201220757%No
201318450%No
201427375%No
201533291%Yes
201627475%No
201733391%Yes
201827375%No
201921258%No
202033592%Yes
202118150%No
202333391%Yes
2024365100%Yes

Latest Records

20
Latest records at Groton
DateStationRecordValueBeat old record byOld record stoodSignificance
30 December 2024Groton, USdaily high min8.9 C (48.0 F)2.8 C (5.0 F)34 years21 of 100 (Routine)
30 December 2024Groton, USdaily high max13.3 C (55.9 F)1.1 C (2.0 F)34 years18 of 100 (Routine)
22 December 2024Groton, USdaily low max-5.6 C (21.9 F)2.3 C (4.1 F)65 years29 of 100 (Routine)
11 December 2024Groton, USdaily rain85.1 mm (3.4 in)28.7 mm (1.1 in)16 years34 of 100 (Routine)
6 November 2024Groton, USdaily high max22.8 C (73.0 F)2.8 C (5.0 F)65 years31 of 100 (Routine)
5 November 2024Groton, USdaily high max (Tie)21.1 C (70.0 F)tie63 years6 of 100 (Routine)
1 November 2024Groton, USdaily high max (Tie)23.9 C (75.0 F)tie42 years4 of 100 (Routine)
31 October 2024Groton, USdaily high max23.3 C (73.9 F)2.2 C (4.0 F)42 years23 of 100 (Routine)
22 October 2024Groton, USdaily high max25.0 C (77.0 F)1.1 C (2.0 F)7 years10 of 100 (Routine)
20 August 2024Groton, USdaily low max (Tie)21.7 C (71.1 F)tie27 years3 of 100 (Routine)
8 August 2024Groton, USdaily low max (Tie)20.0 C (68.0 F)tie49 years5 of 100 (Routine)
31 July 2024Groton, USdaily high min22.8 C (73.0 F)0.6 C (1.1 F)30 years17 of 100 (Routine)
29 July 2024Groton, USdaily low max21.7 C (71.1 F)0.5 C (0.9 F)67 years27 of 100 (Routine)
29 July 2024Groton, USdaily rain44.2 mm (1.7 in)7.4 mm (0.29 in)44 years25 of 100 (Routine)
17 July 2024Groton, USdaily high min (Tie)22.8 C (73.0 F)tie14 years2 of 100 (Routine)
16 July 2024Groton, USdaily high min22.8 C (73.0 F)0.6 C (1.1 F)41 years20 of 100 (Routine)
14 July 2024Groton, USdaily high min (Tie)22.2 C (72.0 F)tie29 years3 of 100 (Routine)
11 July 2024Groton, USdaily high min22.2 C (72.0 F)0.5 C (0.9 F)4 years8 of 100 (Routine)
30 June 2024Groton, USdaily rain51.8 mm (2.0 in)0.5 mm (0.02 in)26 years14 of 100 (Routine)
27 June 2024Groton, USdaily rain44.7 mm (1.8 in)28.7 mm (1.1 in)41 years39 of 100 (Notable)

Climate Trend

45 complete years, 1958 to 2024
Annual mean temperature at Groton as warming stripes, 1958 to 2024 One stripe for each of 45 complete years at Groton, 1958 to 2024. Blue stripes are years cooler than the station's own mean of 10.1 C (50.3 F); red stripes are warmer. The coolest year was 1958, at 8.7 C (47.7 F), and the warmest was 2024, at 12.2 C (53.9 F). The strongest colour marks a difference of 2.1 C (3.8 F). 1958: 8.7 C, -1.4 C from the station mean1959: 10.0 C, -0.1 C from the station mean1960: 9.6 C, -0.5 C from the station mean1961: 9.7 C, -0.5 C from the station mean1962: 8.9 C, -1.3 C from the station mean1963: 9.3 C, -0.9 C from the station mean1964: 9.6 C, -0.6 C from the station mean1965: 9.5 C, -0.7 C from the station mean1966: 9.7 C, -0.5 C from the station mean1967: 9.2 C, -1.0 C from the station mean1968: 9.7 C, -0.5 C from the station mean1969: 9.9 C, -0.2 C from the station mean1970: 9.6 C, -0.6 C from the station mean1971: 10.0 C, -0.1 C from the station mean1972: 9.2 C, -0.9 C from the station mean1973: 10.5 C, +0.3 C from the station mean1974: 10.1 C, -0.1 C from the station mean1975: 10.5 C, +0.3 C from the station mean1976: 9.6 C, -0.5 C from the station mean1977: 9.9 C, -0.3 C from the station mean1978: 9.0 C, -1.1 C from the station mean1979: 10.3 C, +0.1 C from the station mean1980: 10.1 C, -0.1 C from the station mean1981: 10.0 C, -0.1 C from the station mean1982: 10.3 C, +0.2 C from the station mean1983: 11.0 C, +0.8 C from the station mean1984: 10.8 C, +0.6 C from the station mean1985: 10.5 C, +0.4 C from the station mean1986: 10.2 C, +0.1 C from the station mean1987: 10.2 C, 0.0 C from the station mean1990: 11.1 C, +0.9 C from the station mean1991: 11.4 C, +1.3 C from the station mean1993: 10.1 C, -0.1 C from the station mean1994: 9.9 C, -0.2 C from the station mean1995: 10.2 C, +0.1 C from the station mean1996: 9.5 C, -0.6 C from the station mean1997: 9.9 C, -0.2 C from the station mean1999: 10.7 C, +0.6 C from the station mean2000: 9.9 C, -0.2 C from the station mean2002: 11.9 C, +1.7 C from the station mean2003: 10.6 C, +0.4 C from the station mean2004: 10.7 C, +0.6 C from the station mean2008: 11.3 C, +1.2 C from the station mean2011: 11.8 C, +1.6 C from the station mean2024: 12.2 C, +2.0 C from the station mean1958197019801990200020102020
One stripe for each of 45 complete years at Groton, 1958 to 2024. Blue stripes are years cooler than the station's own mean of 10.1 C (50.3 F); red stripes are warmer. The coolest year was 1958, at 8.7 C (47.7 F), and the warmest was 2024, at 12.2 C (53.9 F). The strongest colour marks a difference of 2.1 C (3.8 F).
Annual mean temperature at Groton as warming stripes, 1958 to 2024
YearAnnual mean temperatureDifference from the station mean
19588.7 C-1.40 C
195910.0 C-0.14 C
19609.6 C-0.52 C
19619.7 C-0.47 C
19628.9 C-1.26 C
19639.3 C-0.89 C
19649.6 C-0.55 C
19659.5 C-0.68 C
19669.7 C-0.47 C
19679.2 C-0.96 C
19689.7 C-0.46 C
19699.9 C-0.22 C
19709.6 C-0.55 C
197110.0 C-0.12 C
19729.2 C-0.94 C
197310.5 C+0.34 C
197410.1 C-0.09 C
197510.5 C+0.34 C
19769.6 C-0.54 C
19779.9 C-0.29 C
19789.0 C-1.13 C
197910.3 C+0.11 C
198010.1 C-0.08 C
198110.0 C-0.14 C
198210.3 C+0.18 C
198311.0 C+0.82 C
198410.8 C+0.62 C
198510.5 C+0.40 C
198610.2 C+0.06 C
198710.2 C+0.05 C
199011.1 C+0.93 C
199111.4 C+1.27 C
199310.1 C-0.08 C
19949.9 C-0.20 C
199510.2 C+0.08 C
19969.5 C-0.62 C
19979.9 C-0.22 C
199910.7 C+0.56 C
20009.9 C-0.23 C
200211.9 C+1.72 C
200310.6 C+0.42 C
200410.7 C+0.59 C
200811.3 C+1.20 C
201111.8 C+1.62 C
202412.2 C+2.03 C

The annual mean temperature here has risen by 0.4 C (0.3 to 0.5) per decade over 1958 to 2024. In Fahrenheit: 0.7 F (0.5 to 0.8) per decade. The slope is a straight line fitted to 45 complete years; the brackets give its 95 percent interval.

Fitted temperature trends per decade at Groton
MeasurePer decade (C)Per decade (F)PeriodComplete yearsReading
Annual mean temperature0.4 C (0.3 to 0.5) per decade0.7 F (0.5 to 0.8) per decade1958 to 202445Rise
Mean daily maximum0.2 C (0.1 to 0.3) per decade0.3 F (0.1 to 0.5) per decade1958 to 202445Rise
Mean daily minimum0.6 C (0.5 to 0.7) per decade1.0 F (0.8 to 1.2) per decade1958 to 202445Rise

A year is complete when all 12 months have at least 20 days of both daily maximum and daily minimum readings. The annual mean is the mean of the monthly means. The trend describes this one station over this period; it does not say what caused the change.

Extremes by Year

1948 to 2024
Yearly extremes at Groton: the record and the median year
MeasureRecordYear of the recordMedian yearYears with a value
Hottest day (TXx)38.3 C (100.9 F)199133.1 C (91.5 F)66
Coldest night (TNn)-25.6 C (-14.1 F)1961-18.0 C (-0.5 F)66
Wettest day (Rx1day)188.7 mm (7.4 in)196168.3 mm (2.7 in)75
Wettest five days (Rx5day)297.1 mm (11.7 in)1982105.2 mm (4.1 in)75
Longest dry spell (CDD)39 days194917 days75

Hottest day (TXx)

Hottest day (TXx) at Groton by year The hottest day of the year at Groton, 1948 to 2024. The record is 38.3 C (100.9 F) in 1991, marked on the chart; the median year is 33.1 C (91.5 F). 102030401960198020002020Record: 38.3 C (100.9 F) in 1991
The hottest day of the year at Groton, 1948 to 2024. The record is 38.3 C (100.9 F) in 1991, marked on the chart; the median year is 33.1 C (91.5 F).
Hottest day (TXx) at Groton by year
YearHottest day (TXx)
1948n/a
1949n/a
1950n/a
1951n/a
1952n/a
1953n/a
1954n/a
1955n/a
1956n/a
195735.0 C (95.0 F)
195831.1 C (88.0 F)
195932.2 C (90.0 F)
196031.1 C (88.0 F)
196132.2 C (90.0 F)
196231.1 C (88.0 F)
196334.4 C (93.9 F)
196435.0 C (95.0 F)
196533.3 C (91.9 F)
196636.1 C (97.0 F)
196731.7 C (89.1 F)
196833.9 C (93.0 F)
196934.4 C (93.9 F)
197032.8 C (91.0 F)
197132.8 C (91.0 F)
197232.2 C (90.0 F)
197333.3 C (91.9 F)
197432.8 C (91.0 F)
197537.2 C (99.0 F)
197632.2 C (90.0 F)
197737.2 C (99.0 F)
197833.3 C (91.9 F)
197935.6 C (96.1 F)
198036.7 C (98.1 F)
198134.4 C (93.9 F)
198234.4 C (93.9 F)
198334.4 C (93.9 F)
198433.3 C (91.9 F)
198533.3 C (91.9 F)
198631.7 C (89.1 F)
198733.3 C (91.9 F)
198832.8 C (91.0 F)
198931.1 C (88.0 F)
199031.7 C (89.1 F)
199138.3 C (100.9 F)
199230.6 C (87.1 F)
199334.4 C (93.9 F)
199433.3 C (91.9 F)
199535.0 C (95.0 F)
199631.7 C (89.1 F)
199731.7 C (89.1 F)
199832.8 C (91.0 F)
199936.7 C (98.1 F)
200034.4 C (93.9 F)
200134.4 C (93.9 F)
200235.6 C (96.1 F)
200332.2 C (90.0 F)
200431.1 C (88.0 F)
200514.4 C (57.9 F)
200731.7 C (89.1 F)
200832.8 C (91.0 F)
200932.2 C (90.0 F)
201036.7 C (98.1 F)
201136.1 C (97.0 F)
201232.8 C (91.0 F)
201331.7 C (89.1 F)
201430.6 C (87.1 F)
201532.2 C (90.0 F)
201633.3 C (91.9 F)
201732.8 C (91.0 F)
201833.3 C (91.9 F)
201933.9 C (93.0 F)
202033.3 C (91.9 F)
202132.2 C (90.0 F)
202332.2 C (90.0 F)
202431.7 C (89.1 F)

Coldest night (TNn)

Coldest night (TNn) at Groton by year The coldest night of the year at Groton, 1948 to 2024. The record is -25.6 C (-14.1 F) in 1961, marked on the chart; the median year is -18.0 C (-0.5 F). -30-25-20-15-10-51960198020002020Record: -25.6 C (-14.1 F) in 1961
The coldest night of the year at Groton, 1948 to 2024. The record is -25.6 C (-14.1 F) in 1961, marked on the chart; the median year is -18.0 C (-0.5 F).
Coldest night (TNn) at Groton by year
YearColdest night (TNn)
1948n/a
1949n/a
1950n/a
1951n/a
1952n/a
1953n/a
1954n/a
1955n/a
1956n/a
1957-11.1 C (12.0 F)
1958-19.4 C (-2.9 F)
1959-16.7 C (1.9 F)
1960-16.1 C (3.0 F)
1961-25.6 C (-14.1 F)
1962-23.3 C (-9.9 F)
1963-21.1 C (-6.0 F)
1964-15.6 C (3.9 F)
1965-24.4 C (-11.9 F)
1966-16.1 C (3.0 F)
1967-22.8 C (-9.0 F)
1968-22.2 C (-8.0 F)
1969-15.6 C (3.9 F)
1970-20.0 C (-4.0 F)
1971-19.4 C (-2.9 F)
1972-17.2 C (1.0 F)
1973-17.8 C (0.0 F)
1974-18.3 C (-0.9 F)
1975-16.7 C (1.9 F)
1976-20.0 C (-4.0 F)
1977-20.0 C (-4.0 F)
1978-23.3 C (-9.9 F)
1979-23.9 C (-11.0 F)
1980-23.3 C (-9.9 F)
1981-23.9 C (-11.0 F)
1982-25.0 C (-13.0 F)
1983-18.3 C (-0.9 F)
1984-23.9 C (-11.0 F)
1985-17.2 C (1.0 F)
1986-17.2 C (1.0 F)
1987-17.8 C (0.0 F)
1988-20.6 C (-5.1 F)
1989-21.7 C (-7.1 F)
1990-16.1 C (3.0 F)
1991-21.1 C (-6.0 F)
1992-15.6 C (3.9 F)
1993-18.9 C (-2.0 F)
1994-20.6 C (-5.1 F)
1995-17.8 C (0.0 F)
1996-22.8 C (-9.0 F)
1997-18.3 C (-0.9 F)
1998-12.8 C (9.0 F)
1999-16.7 C (1.9 F)
2000-17.2 C (1.0 F)
2001-14.4 C (6.1 F)
2002-11.1 C (12.0 F)
2003-20.0 C (-4.0 F)
2004-19.4 C (-2.9 F)
2005-18.3 C (-0.9 F)
2007-15.6 C (3.9 F)
2008-13.3 C (8.1 F)
2009-21.1 C (-6.0 F)
2010-14.4 C (6.1 F)
2011-17.2 C (1.0 F)
2012-11.7 C (10.9 F)
2013-9.4 C (15.1 F)
2014-13.9 C (7.0 F)
2015-20.6 C (-5.1 F)
2016-22.2 C (-8.0 F)
2017-12.2 C (10.0 F)
2018-10.6 C (12.9 F)
2019-17.2 C (1.0 F)
2020-11.7 C (10.9 F)
2021-12.8 C (9.0 F)
2023-21.1 C (-6.0 F)
2024-13.3 C (8.1 F)

Wettest day (Rx1day)

Wettest day (Rx1day) at Groton by year The wettest day of the year at Groton, 1948 to 2024. The record is 188.7 mm (7.4 in) in 1961, marked on the chart; the median year is 68.3 mm (2.7 in). 0501001502001960198020002020Record: 188.7 mm (7.4 in) in 1961
The wettest day of the year at Groton, 1948 to 2024. The record is 188.7 mm (7.4 in) in 1961, marked on the chart; the median year is 68.3 mm (2.7 in).
Wettest day (Rx1day) at Groton by year
YearWettest day (Rx1day)
194841.7 mm (1.6 in)
194947.2 mm (1.9 in)
195036.1 mm (1.4 in)
195184.3 mm (3.3 in)
1952121.9 mm (4.8 in)
195369.1 mm (2.7 in)
1954156.2 mm (6.1 in)
1955130.6 mm (5.1 in)
195653.3 mm (2.1 in)
195751.8 mm (2.0 in)
195872.1 mm (2.8 in)
195968.6 mm (2.7 in)
196082.3 mm (3.2 in)
1961188.7 mm (7.4 in)
1962122.4 mm (4.8 in)
196352.1 mm (2.1 in)
196452.8 mm (2.1 in)
196534.5 mm (1.4 in)
196658.2 mm (2.3 in)
196789.2 mm (3.5 in)
196865.0 mm (2.6 in)
196968.6 mm (2.7 in)
197076.2 mm (3.0 in)
1971113.8 mm (4.5 in)
1972124.5 mm (4.9 in)
197385.9 mm (3.4 in)
197453.1 mm (2.1 in)
197559.4 mm (2.3 in)
197660.5 mm (2.4 in)
197769.3 mm (2.7 in)
197848.5 mm (1.9 in)
197967.1 mm (2.6 in)
198054.6 mm (2.1 in)
198152.3 mm (2.1 in)
1982160.0 mm (6.3 in)
198377.5 mm (3.1 in)
198460.7 mm (2.4 in)
1985107.4 mm (4.2 in)
198693.5 mm (3.7 in)
198755.9 mm (2.2 in)
198884.8 mm (3.3 in)
198999.1 mm (3.9 in)
1990119.4 mm (4.7 in)
1991116.1 mm (4.6 in)
199274.4 mm (2.9 in)
199375.7 mm (3.0 in)
199465.5 mm (2.6 in)
199587.1 mm (3.4 in)
199665.5 mm (2.6 in)
199740.6 mm (1.6 in)
199888.4 mm (3.5 in)
199988.1 mm (3.5 in)
200065.3 mm (2.6 in)
2001120.7 mm (4.8 in)
200251.1 mm (2.0 in)
200361.7 mm (2.4 in)
200483.6 mm (3.3 in)
200518.0 mm (0.7 in)
200766.3 mm (2.6 in)
200897.3 mm (3.8 in)
2009111.3 mm (4.4 in)
201048.3 mm (1.9 in)
201170.9 mm (2.8 in)
201236.1 mm (1.4 in)
201345.5 mm (1.8 in)
201462.5 mm (2.5 in)
201558.4 mm (2.3 in)
201655.1 mm (2.2 in)
201768.3 mm (2.7 in)
201852.3 mm (2.1 in)
201967.6 mm (2.7 in)
202053.3 mm (2.1 in)
202150.8 mm (2.0 in)
202374.9 mm (2.9 in)
202485.1 mm (3.4 in)

Wettest five days (Rx5day)

Wettest five days (Rx5day) at Groton by year The wettest five days of the year at Groton, 1948 to 2024. The record is 297.1 mm (11.7 in) in 1982, marked on the chart; the median year is 105.2 mm (4.1 in). 01002003001960198020002020Record: 297.1 mm (11.7 in) in 1982
The wettest five days of the year at Groton, 1948 to 2024. The record is 297.1 mm (11.7 in) in 1982, marked on the chart; the median year is 105.2 mm (4.1 in).
Wettest five days (Rx5day) at Groton by year
YearWettest five days (Rx5day)
194855.5 mm (2.2 in)
194966.0 mm (2.6 in)
195053.1 mm (2.1 in)
1951122.9 mm (4.8 in)
1952184.0 mm (7.2 in)
1953117.1 mm (4.6 in)
1954169.4 mm (6.7 in)
1955160.1 mm (6.3 in)
195670.4 mm (2.8 in)
195799.1 mm (3.9 in)
1958113.5 mm (4.5 in)
1959127.4 mm (5.0 in)
1960105.0 mm (4.1 in)
1961202.2 mm (8.0 in)
1962131.1 mm (5.2 in)
196376.5 mm (3.0 in)
196497.5 mm (3.8 in)
196557.2 mm (2.3 in)
196670.3 mm (2.8 in)
1967109.0 mm (4.3 in)
1968101.9 mm (4.0 in)
1969109.5 mm (4.3 in)
1970148.1 mm (5.8 in)
1971123.7 mm (4.9 in)
1972171.7 mm (6.8 in)
197388.4 mm (3.5 in)
197464.8 mm (2.6 in)
197599.6 mm (3.9 in)
1976105.7 mm (4.2 in)
197787.4 mm (3.4 in)
197873.9 mm (2.9 in)
1979129.9 mm (5.1 in)
1980124.5 mm (4.9 in)
198175.2 mm (3.0 in)
1982297.1 mm (11.7 in)
1983105.2 mm (4.1 in)
1984123.3 mm (4.9 in)
1985177.5 mm (7.0 in)
1986110.5 mm (4.4 in)
198797.0 mm (3.8 in)
1988144.1 mm (5.7 in)
1989141.7 mm (5.6 in)
1990125.0 mm (4.9 in)
1991144.6 mm (5.7 in)
199292.1 mm (3.6 in)
199383.8 mm (3.3 in)
1994108.7 mm (4.3 in)
199594.2 mm (3.7 in)
1996114.0 mm (4.5 in)
199766.6 mm (2.6 in)
1998137.4 mm (5.4 in)
1999112.9 mm (4.4 in)
200081.3 mm (3.2 in)
2001120.7 mm (4.8 in)
200283.6 mm (3.3 in)
200381.3 mm (3.2 in)
200497.1 mm (3.8 in)
200541.2 mm (1.6 in)
2007107.2 mm (4.2 in)
2008114.5 mm (4.5 in)
2009119.7 mm (4.7 in)
2010107.7 mm (4.2 in)
2011117.4 mm (4.6 in)
201266.5 mm (2.6 in)
201354.9 mm (2.2 in)
201496.1 mm (3.8 in)
201585.8 mm (3.4 in)
201672.7 mm (2.9 in)
2017150.6 mm (5.9 in)
201883.8 mm (3.3 in)
201988.4 mm (3.5 in)
202065.1 mm (2.6 in)
202183.5 mm (3.3 in)
202392.3 mm (3.6 in)
2024129.8 mm (5.1 in)

Longest dry spell (CDD)

Longest dry spell (CDD) at Groton by year The longest dry spell of the year at Groton, 1948 to 2024. The record is 39 days in 1949, marked on the chart; the median year is 17 days. 0102030401960198020002020Record: 39 days in 1949
The longest dry spell of the year at Groton, 1948 to 2024. The record is 39 days in 1949, marked on the chart; the median year is 17 days.
Longest dry spell (CDD) at Groton by year
YearLongest dry spell (CDD)
194823 days
194939 days
195011 days
195112 days
195222 days
195319 days
195413 days
195516 days
195623 days
195717 days
195821 days
195916 days
196018 days
196115 days
196216 days
196328 days
196419 days
196537 days
196615 days
196716 days
196822 days
196917 days
197015 days
197117 days
197212 days
197316 days
197416 days
197515 days
197620 days
197717 days
197819 days
197921 days
198024 days
198117 days
198221 days
198322 days
198420 days
198517 days
198618 days
198723 days
198816 days
198914 days
199012 days
199113 days
199217 days
199313 days
199417 days
199537 days
199611 days
199717 days
199816 days
199923 days
200011 days
200117 days
200217 days
200323 days
200425 days
20054 days
200720 days
200817 days
200914 days
201014 days
201116 days
201214 days
201323 days
201417 days
201519 days
201615 days
201712 days
201813 days
201914 days
202019 days
202117 days
202320 days
202424 days

Each chart shows one value per year; the dot marks the record year. TXx is the hottest daily maximum, TNn the coldest daily minimum, Rx1day and Rx5day the largest one-day and five-day rain totals, and CDD the longest run of days with less than 1 mm of rain. A year with missing days can understate an extreme.

Frost Dates and Growing Season

45 years with a frost

Across 45 years with a frost, the median last spring frost at Groton falls on 19 April and the median first autumn frost on 21 October, which leaves a median of 185 days between them.

Fitted over all years, the growing season changes by +7.0 days per decade at this station.

Frost dates and growing season at Groton
MeasureMedian, all yearsEarliest periodRecent period (1973 to 2024)Recent against earliestFitted trend
Last spring frost19 Apriln/a14 Apriln/a-4.5 days per decade
First autumn frost21 Octobern/a22 Octobern/a+2.5 days per decade
Growing days185 daysn/a191 daysn/a+7.0 days per decade

A frost day is a day with a daily minimum at or below 0 C (32 F). The last spring frost and the first autumn frost are the last and first such days of the cold season, and growing days are the days between them. A negative trend for the last spring frost means it comes earlier.

Rainfall Return Levels

63 years, 1949 to 2024

A day with at least 72.5 mm (2.9 in) of rain is expected about once in 2 years. A day with at least 194.8 mm (7.7 in) of rain is expected about once in 100 years.

Rainfall return levels at Groton: the daily rain expected about once in a given number of years
Expected about once inA day with at leastNote
2 years72.5 mm (2.9 in)
5 years99.0 mm (3.9 in)
10 years118.9 mm (4.7 in)
25 years146.8 mm (5.8 in)
50 years169.8 mm (6.7 in)
100 years194.8 mm (7.7 in)Longer than the 63 years of record

The levels come from a generalised extreme value (GEV) distribution fitted by L-moments to the wettest-day total of each year, 63 years of values from 1949 to 2024.

A return level is an estimate. It is least reliable for the long periods, 50 and 100 years, and for any period longer than the record behind the fit, where the fit has to reach past the largest day actually observed. It is not a forecast.

The largest wettest-day totals in the fit: 188.7 mm (7.4 in) in 1961; 160.0 mm (6.3 in) in 1982; 156.2 mm (6.1 in) in 1954.

Station Changes

No change in the annual mean temperature of this station was found against its neighbours.

Download the Data

  • Data for Groton standing records by year: CSV or JSON. Field meanings are on the data page.
  • Data for Groton threshold days by year: CSV or JSON. Field meanings are on the data page.

Source: NOAA National Centers for Environmental Information, Global Historical Climatology Network Daily (GHCN-Daily). Records are computed by World Extreme Weather Monitor and are not official NOAA products. (US Government open data (NOAA NCEI)) Data as of 2026-10-17 (17 October 2026). Records are computed by this site and are not official.

Data as of . Last revised (2025-12-31).