Alton Weather Records (CA006150243)

Record envelope, standing records and threshold days for Alton (CA006150243), Ontario, Canada, with 78 years of record.

Key Facts for Alton

Alton (CA006150243) is a weather station in Ontario, Canada at 43.85 latitude and -80.08 longitude, 401 m (1,316 ft) above sea level.
The station reports from 1887 to 1964, 78 years of record.
1,464 records set at Alton still stand.
Records are tracked for tmax, tmin, prcp, snow: an element needs 30 years of data to be eligible.
Alton set a daily record high minimum temperature of 0.6 C (33.1 F) on 20 January 1964.

About the Station

Location: Ontario, Canada, 43.85 latitude, -80.08 longitude.
Elevation: 401 m (1,316 ft).
Period of record: 1887 to 1964, 78 years.
Eligible elements: tmax, tmin, prcp, snow.

Daily Record Envelope and 2026

0 days at or beyond a record

The band shows the record high and record low for each calendar day at Alton. 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 Alton, with 2026 drawn through them
Month	Highest record high	Lowest record low	2026 highest maximum	2026 lowest minimum
Jan	15.0 C (59.0 F)	-33.9 C (-29.0 F)	n/a	n/a
Feb	17.2 C (63.0 F)	-35.6 C (-32.1 F)	n/a	n/a
Mar	27.2 C (81.0 F)	-30.6 C (-23.1 F)	n/a	n/a
Apr	28.9 C (84.0 F)	-20.6 C (-5.1 F)	n/a	n/a
May	32.8 C (91.0 F)	-7.8 C (18.0 F)	n/a	n/a
Jun	36.1 C (97.0 F)	-6.7 C (19.9 F)	n/a	n/a
Jul	38.3 C (100.9 F)	1.1 C (34.0 F)	n/a	n/a
Aug	37.2 C (99.0 F)	-1.7 C (28.9 F)	n/a	n/a
Sep	36.1 C (97.0 F)	-6.1 C (21.0 F)	n/a	n/a
Oct	32.2 C (90.0 F)	-13.3 C (8.1 F)	n/a	n/a
Nov	23.3 C (73.9 F)	-22.2 C (-8.0 F)	n/a	n/a
Dec	13.3 C (55.9 F)	-31.7 C (-25.1 F)	n/a	n/a

Which Years Hold Standing Records

1,464 standing records

1,464 records at Alton still stand. 1904 holds the most, with 52.

Standing records at Alton by the year they were set
Year set	Standing records
1887	26
1888	36
1889	24
1890	27
1891	25
1892	19
1893	12
1894	25
1895	51
1896	34
1897	19
1898	23
1899	31
1900	42
1901	15
1902	22
1903	30
1904	52
1905	18
1906	26
1907	25
1908	25
1909	24
1910	34
1911	34
1912	36
1913	34
1914	31
1915	17
1916	32
1917	17
1918	27
1919	18
1920	24
1921	29
1922	13
1923	25
1924	23
1925	29
1926	13
1927	23
1928	11
1929	23
1930	31
1931	28
1932	12
1933	37
1934	21
1935	16
1947	15
1948	21
1949	36
1950	19
1951	13
1952	15
1953	12
1954	10
1955	5
1959	4
1961	7
1962	18
1963	18
1964	2

All-Time Record Progression

3 new records

3 all-time records were set at Alton between 29 January 1930 and 26 August 1949. Each dot is a new record.

When Alton set new all-time records
Date	Kind	Detail
1930-01-29	Record daily snowfall	Record daily snowfall 71.1 cm (28.0 in)
1934-02-09	Record low maximum temperature	Record low maximum temperature -26.7 C (-16.1 F)
1949-08-26	Record high minimum temperature	Record high minimum temperature 24.4 C (75.9 F)

Wettest Day of Each Month

Sep: 104.4 mm (4.1 in)

The wettest day on record for each calendar month at Alton. The most was 104.4 mm (4.1 in) on 24 September 1904.

Record daily precipitation for each month at Alton
Month	Record daily precipitation (mm)	Date
Jan	71.1 mm (2.8 in)	29 January 1930
Feb	55.9 mm (2.2 in)	15 February 1954
Mar	35.6 mm (1.4 in)	7 March 1931
Apr	48.8 mm (1.9 in)	23 April 1921
May	72.9 mm (2.9 in)	22 May 1912
Jun	70.1 mm (2.8 in)	5 June 1890
Jul	63.5 mm (2.5 in)	19 July 1921
Aug	87.6 mm (3.4 in)	9 August 1891
Sep	104.4 mm (4.1 in)	24 September 1904
Oct	57.2 mm (2.3 in)	12 October 1949
Nov	76.5 mm (3.0 in)	5 November 1935
Dec	52.1 mm (2.1 in)	16 December 1893

Period of Record Coverage

1887 to 1964

63 years of record at Alton, 1887 to 1964. 8 years have data for under 90 percent of days and are left out of rankings: 1935, 1949, 1950, 1954, 1955, 1959, 1961, 1964.

Days with data per year at Alton
Year	Days with data	Share of year	Complete
1887	364	100%	Yes
1888	366	100%	Yes
1889	365	100%	Yes
1890	365	100%	Yes
1891	365	100%	Yes
1892	366	100%	Yes
1893	363	99%	Yes
1894	364	100%	Yes
1895	365	100%	Yes
1896	366	100%	Yes
1897	365	100%	Yes
1898	365	100%	Yes
1899	365	100%	Yes
1900	365	100%	Yes
1901	365	100%	Yes
1902	365	100%	Yes
1903	365	100%	Yes
1904	365	100%	Yes
1905	365	100%	Yes
1906	365	100%	Yes
1907	365	100%	Yes
1908	366	100%	Yes
1909	365	100%	Yes
1910	364	100%	Yes
1911	365	100%	Yes
1912	366	100%	Yes
1913	364	100%	Yes
1914	365	100%	Yes
1915	365	100%	Yes
1916	366	100%	Yes
1917	365	100%	Yes
1918	365	100%	Yes
1919	365	100%	Yes
1920	365	100%	Yes
1921	365	100%	Yes
1922	365	100%	Yes
1923	363	99%	Yes
1924	366	100%	Yes
1925	365	100%	Yes
1926	334	92%	Yes
1927	364	100%	Yes
1928	366	100%	Yes
1929	365	100%	Yes
1930	364	100%	Yes
1931	365	100%	Yes
1932	365	100%	Yes
1933	365	100%	Yes
1934	365	100%	Yes
1935	309	85%	No
1947	333	91%	Yes
1948	366	100%	Yes
1949	306	84%	No
1950	275	75%	No
1951	365	100%	Yes
1952	336	92%	Yes
1953	333	91%	Yes
1954	210	58%	No
1955	123	34%	No
1959	61	17%	No
1961	184	50%	No
1962	365	100%	Yes
1963	334	92%	Yes
1964	31	8%	No

Latest Records

Latest records at Alton
Date	Station	Record	Value	Beat old record by	Old record stood	Significance
20 January 1964	Alton, CA	daily high min	0.6 C (33.1 F)	1.7 C (3.1 F)	63 years	28 of 100 (Routine)
1 January 1964	Alton, CA	daily low min	-25.0 C (-13.0 F)	1.1 C (2.0 F)	64 years	27 of 100 (Routine)
21 December 1963	Alton, CA	daily low min	-26.1 C (-15.0 F)	3.9 C (7.0 F)	61 years	31 of 100 (Routine)
25 October 1963	Alton, CA	daily high max	23.9 C (75.0 F)	1.1 C (2.0 F)	63 years	27 of 100 (Routine)
24 October 1963	Alton, CA	daily high max	24.4 C (75.9 F)	2.2 C (4.0 F)	62 years	28 of 100 (Routine)
23 October 1963	Alton, CA	daily high max	24.4 C (75.9 F)	2.7 C (4.9 F)	42 years	23 of 100 (Routine)
23 October 1963	Alton, CA	daily high min (Tie)	10.0 C (50.0 F)	tie	62 years	6 of 100 (Routine)
7 October 1963	Alton, CA	daily high min (Tie)	16.7 C (62.1 F)	tie	62 years	6 of 100 (Routine)
24 September 1963	Alton, CA	daily low min	-3.9 C (25.0 F)	0.6 C (1.1 F)	75 years	30 of 100 (Routine)
13 September 1963	Alton, CA	daily low min	-0.6 C (30.9 F)	1.7 C (3.1 F)	58 years	27 of 100 (Routine)
4 September 1963	Alton, CA	daily low max	16.1 C (61.0 F)	0.6 C (1.1 F)	10 years	11 of 100 (Routine)
18 August 1963	Alton, CA	daily low min	4.4 C (39.9 F)	0.6 C (1.1 F)	1 year	8 of 100 (Routine)
13 August 1963	Alton, CA	daily rain	50.8 mm (2.0 in)	4.1 mm (0.16 in)	62 years	28 of 100 (Routine)
14 July 1963	Alton, CA	daily low max	16.7 C (62.1 F)	3.3 C (5.9 F)	67 years	35 of 100 (Notable)
14 July 1963	Alton, CA	daily rain	16.3 mm (0.6 in)	2.3 mm (0.09 in)	34 years	18 of 100 (Routine)
9 July 1963	Alton, CA	daily low min (Tie)	4.4 C (39.9 F)	tie	71 years	7 of 100 (Routine)
10 June 1963	Alton, CA	daily low max	11.1 C (52.0 F)	1.7 C (3.1 F)	44 years	23 of 100 (Routine)
25 May 1963	Alton, CA	daily low min	-1.7 C (28.9 F)	1.7 C (3.1 F)	33 years	20 of 100 (Routine)
24 May 1963	Alton, CA	daily low min	-5.0 C (23.0 F)	1.7 C (3.1 F)	71 years	31 of 100 (Routine)
30 April 1963	Alton, CA	daily snowfall	2.5 cm (1.0 in)	2.5 cm (1.0 in)	75 years	20 of 100 (Routine)

Climate Trend

49 complete years, 1887 to 1962

One stripe for each of 49 complete years at Alton, 1887 to 1962. Blue stripes are years cooler than the station's own mean of 5.3 C (41.5 F); red stripes are warmer. The coolest year was 1904, at 3.0 C (37.5 F), and the warmest was 1921, at 7.4 C (45.3 F). The strongest colour marks a difference of 2.3 C (4.1 F).

Annual mean temperature at Alton as warming stripes, 1887 to 1962
Year	Annual mean temperature	Difference from the station mean
1887	4.9 C	-0.40 C
1888	3.7 C	-1.61 C
1889	5.3 C	-0.02 C
1890	4.9 C	-0.36 C
1891	5.5 C	+0.22 C
1892	4.5 C	-0.81 C
1893	4.2 C	-1.13 C
1894	5.9 C	+0.59 C
1895	4.4 C	-0.92 C
1896	5.2 C	-0.12 C
1897	5.4 C	+0.13 C
1898	6.3 C	+1.00 C
1899	5.3 C	-0.01 C
1900	6.5 C	+1.18 C
1901	5.1 C	-0.23 C
1902	5.2 C	-0.12 C
1903	5.1 C	-0.24 C
1904	3.0 C	-2.26 C
1905	4.5 C	-0.79 C
1906	5.2 C	-0.13 C
1907	4.0 C	-1.30 C
1908	5.2 C	-0.10 C
1909	4.7 C	-0.59 C
1910	4.5 C	-0.81 C
1911	5.3 C	+0.03 C
1912	3.6 C	-1.75 C
1913	5.9 C	+0.60 C
1914	5.7 C	+0.35 C
1915	5.6 C	+0.32 C
1916	5.5 C	+0.23 C
1917	3.5 C	-1.82 C
1918	5.3 C	-0.05 C
1919	6.2 C	+0.93 C
1920	5.2 C	-0.06 C
1921	7.4 C	+2.11 C
1922	6.7 C	+1.36 C
1923	5.6 C	+0.25 C
1924	5.3 C	-0.03 C
1925	5.9 C	+0.62 C
1927	5.8 C	+0.47 C
1928	5.8 C	+0.45 C
1929	5.4 C	+0.05 C
1930	6.5 C	+1.22 C
1931	7.0 C	+1.73 C
1932	6.3 C	+1.00 C
1933	6.5 C	+1.18 C
1934	5.2 C	-0.07 C
1951	5.0 C	-0.28 C
1962	5.4 C	+0.07 C

The annual mean temperature here has risen by 0.20 C (0.05 to 0.34) per decade over 1887 to 1962. In Fahrenheit: 0.4 F (0.1 to 0.6) per decade. The slope is a straight line fitted to 49 complete years; the brackets give its 95 percent interval.

Fitted temperature trends per decade at Alton
Measure	Per decade (C)	Per decade (F)	Period	Complete years	Reading
Annual mean temperature	0.20 C (0.05 to 0.34) per decade	0.4 F (0.1 to 0.6) per decade	1887 to 1962	49	Rise
Mean daily maximum	0.16 C (0.00 to 0.32) per decade	0.29 F (-0.01 to 0.58) per decade	1887 to 1962	49	Not clearly different from zero
Mean daily minimum	0.23 C (0.05 to 0.42) per decade	0.4 F (0.1 to 0.7) per decade	1887 to 1962	49	Rise

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

1887 to 1964

Yearly extremes at Alton: the record and the median year
Measure	Record	Year of the record	Median year	Years with a value
Hottest day (TXx)	38.3 C (100.9 F)	1911	33.3 C (91.9 F)	63
Coldest night (TNn)	-35.6 C (-32.1 F)	1908	-28.3 C (-18.9 F)	63
Wettest day (Rx1day)	104.4 mm (4.1 in)	1904	49.8 mm (2.0 in)	62
Wettest five days (Rx5day)	114.4 mm (4.5 in)	1889	68.9 mm (2.7 in)	62
Longest dry spell (CDD)	39 days	1908	17 days	62

Hottest day (TXx)

The hottest day of the year at Alton, 1887 to 1964. The record is 38.3 C (100.9 F) in 1911, marked on the chart; the median year is 33.3 C (91.9 F).

Hottest day (TXx) at Alton by year
Year	Hottest day (TXx)
1887	33.9 C (93.0 F)
1888	33.3 C (91.9 F)
1889	32.2 C (90.0 F)
1890	33.3 C (91.9 F)
1891	31.7 C (89.1 F)
1892	32.2 C (90.0 F)
1893	33.3 C (91.9 F)
1894	33.9 C (93.0 F)
1895	32.8 C (91.0 F)
1896	33.3 C (91.9 F)
1897	34.4 C (93.9 F)
1898	35.0 C (95.0 F)
1899	35.0 C (95.0 F)
1900	35.6 C (96.1 F)
1901	34.4 C (93.9 F)
1902	31.1 C (88.0 F)
1903	32.2 C (90.0 F)
1904	32.2 C (90.0 F)
1905	32.2 C (90.0 F)
1906	31.1 C (88.0 F)
1907	32.8 C (91.0 F)
1908	33.3 C (91.9 F)
1909	32.2 C (90.0 F)
1910	33.3 C (91.9 F)
1911	38.3 C (100.9 F)
1912	32.8 C (91.0 F)
1913	35.0 C (95.0 F)
1914	35.6 C (96.1 F)
1915	29.4 C (84.9 F)
1916	36.7 C (98.1 F)
1917	34.4 C (93.9 F)
1918	37.2 C (99.0 F)
1919	34.4 C (93.9 F)
1920	32.2 C (90.0 F)
1921	35.0 C (95.0 F)
1922	33.3 C (91.9 F)
1923	32.8 C (91.0 F)
1924	32.2 C (90.0 F)
1925	35.0 C (95.0 F)
1926	32.8 C (91.0 F)
1927	33.9 C (93.0 F)
1928	31.1 C (88.0 F)
1929	33.3 C (91.9 F)
1930	33.9 C (93.0 F)
1931	36.7 C (98.1 F)
1932	33.9 C (93.0 F)
1933	35.6 C (96.1 F)
1934	36.1 C (97.0 F)
1935	33.3 C (91.9 F)
1947	30.0 C (86.0 F)
1948	33.9 C (93.0 F)
1949	33.9 C (93.0 F)
1950	28.9 C (84.0 F)
1951	31.1 C (88.0 F)
1952	33.3 C (91.9 F)
1953	35.0 C (95.0 F)
1954	30.6 C (87.1 F)
1955	32.8 C (91.0 F)
1959	18.3 C (64.9 F)
1961	30.6 C (87.1 F)
1962	31.1 C (88.0 F)
1963	32.8 C (91.0 F)
1964	6.1 C (43.0 F)

Coldest night (TNn)

The coldest night of the year at Alton, 1887 to 1964. The record is -35.6 C (-32.1 F) in 1908, marked on the chart; the median year is -28.3 C (-18.9 F).

Coldest night (TNn) at Alton by year
Year	Coldest night (TNn)
1887	-24.4 C (-11.9 F)
1888	-30.6 C (-23.1 F)
1889	-27.2 C (-17.0 F)
1890	-23.9 C (-11.0 F)
1891	-22.2 C (-8.0 F)
1892	-25.6 C (-14.1 F)
1893	-26.7 C (-16.1 F)
1894	-30.0 C (-22.0 F)
1895	-32.8 C (-27.0 F)
1896	-33.9 C (-29.0 F)
1897	-28.3 C (-18.9 F)
1898	-30.0 C (-22.0 F)
1899	-29.4 C (-20.9 F)
1900	-28.9 C (-20.0 F)
1901	-29.4 C (-20.9 F)
1902	-22.2 C (-8.0 F)
1903	-28.9 C (-20.0 F)
1904	-33.9 C (-29.0 F)
1905	-29.4 C (-20.9 F)
1906	-30.6 C (-23.1 F)
1907	-29.4 C (-20.9 F)
1908	-35.6 C (-32.1 F)
1909	-28.3 C (-18.9 F)
1910	-33.3 C (-27.9 F)
1911	-25.0 C (-13.0 F)
1912	-35.6 C (-32.1 F)
1913	-26.1 C (-15.0 F)
1914	-32.8 C (-27.0 F)
1915	-23.3 C (-9.9 F)
1916	-31.1 C (-24.0 F)
1917	-30.6 C (-23.1 F)
1918	-33.3 C (-27.9 F)
1919	-26.7 C (-16.1 F)
1920	-30.6 C (-23.1 F)
1921	-25.0 C (-13.0 F)
1922	-26.1 C (-15.0 F)
1923	-25.6 C (-14.1 F)
1924	-27.8 C (-18.0 F)
1925	-32.2 C (-26.0 F)
1926	-23.9 C (-11.0 F)
1927	-30.6 C (-23.1 F)
1928	-26.1 C (-15.0 F)
1929	-26.1 C (-15.0 F)
1930	-27.2 C (-17.0 F)
1931	-26.1 C (-15.0 F)
1932	-22.2 C (-8.0 F)
1933	-31.7 C (-25.1 F)
1934	-33.9 C (-29.0 F)
1935	-30.0 C (-22.0 F)
1947	-17.2 C (1.0 F)
1948	-31.7 C (-25.1 F)
1949	-20.6 C (-5.1 F)
1950	-26.1 C (-15.0 F)
1951	-26.7 C (-16.1 F)
1952	-28.9 C (-20.0 F)
1953	-20.6 C (-5.1 F)
1954	-26.7 C (-16.1 F)
1955	-23.3 C (-9.9 F)
1959	-19.4 C (-2.9 F)
1961	-20.0 C (-4.0 F)
1962	-30.6 C (-23.1 F)
1963	-28.9 C (-20.0 F)
1964	-25.0 C (-13.0 F)

Wettest day (Rx1day)

The wettest day of the year at Alton, 1887 to 1964. The record is 104.4 mm (4.1 in) in 1904, marked on the chart; the median year is 49.8 mm (2.0 in).

Wettest day (Rx1day) at Alton by year
Year	Wettest day (Rx1day)
1887	48.5 mm (1.9 in)
1888	58.9 mm (2.3 in)
1889	71.4 mm (2.8 in)
1890	70.1 mm (2.8 in)
1891	87.6 mm (3.4 in)
1892	53.6 mm (2.1 in)
1893	52.6 mm (2.1 in)
1894	36.3 mm (1.4 in)
1895	51.6 mm (2.0 in)
1896	40.1 mm (1.6 in)
1897	47.2 mm (1.9 in)
1898	42.2 mm (1.7 in)
1899	70.6 mm (2.8 in)
1900	46.7 mm (1.8 in)
1901	61.7 mm (2.4 in)
1902	39.9 mm (1.6 in)
1903	36.1 mm (1.4 in)
1904	104.4 mm (4.1 in)
1905	64.8 mm (2.6 in)
1906	48.3 mm (1.9 in)
1907	38.9 mm (1.5 in)
1908	58.7 mm (2.3 in)
1909	60.5 mm (2.4 in)
1910	35.6 mm (1.4 in)
1911	50.8 mm (2.0 in)
1912	72.9 mm (2.9 in)
1913	40.9 mm (1.6 in)
1914	35.6 mm (1.4 in)
1915	71.6 mm (2.8 in)
1916	54.4 mm (2.1 in)
1917	41.1 mm (1.6 in)
1918	43.2 mm (1.7 in)
1919	33.5 mm (1.3 in)
1920	48.8 mm (1.9 in)
1921	63.5 mm (2.5 in)
1922	40.6 mm (1.6 in)
1923	52.1 mm (2.1 in)
1924	33.0 mm (1.3 in)
1925	22.4 mm (0.9 in)
1926	50.8 mm (2.0 in)
1927	40.6 mm (1.6 in)
1928	53.8 mm (2.1 in)
1929	47.5 mm (1.9 in)
1930	71.1 mm (2.8 in)
1931	38.4 mm (1.5 in)
1932	58.4 mm (2.3 in)
1933	28.4 mm (1.1 in)
1934	38.1 mm (1.5 in)
1935	76.5 mm (3.0 in)
1947	47.0 mm (1.9 in)
1948	35.6 mm (1.4 in)
1949	57.2 mm (2.3 in)
1950	35.6 mm (1.4 in)
1951	43.2 mm (1.7 in)
1952	36.8 mm (1.4 in)
1953	50.8 mm (2.0 in)
1954	55.9 mm (2.2 in)
1955	50.8 mm (2.0 in)
1959	32.0 mm (1.3 in)
1961	52.1 mm (2.1 in)
1962	54.6 mm (2.1 in)
1963	50.8 mm (2.0 in)
1964	n/a

Wettest five days (Rx5day)

The wettest five days of the year at Alton, 1887 to 1964. The record is 114.4 mm (4.5 in) in 1889, marked on the chart; the median year is 68.9 mm (2.7 in).

Wettest five days (Rx5day) at Alton by year
Year	Wettest five days (Rx5day)
1887	64.8 mm (2.6 in)
1888	89.6 mm (3.5 in)
1889	114.4 mm (4.5 in)
1890	87.1 mm (3.4 in)
1891	88.6 mm (3.5 in)
1892	63.5 mm (2.5 in)
1893	69.9 mm (2.8 in)
1894	81.0 mm (3.2 in)
1895	54.1 mm (2.1 in)
1896	59.7 mm (2.4 in)
1897	76.1 mm (3.0 in)
1898	56.9 mm (2.2 in)
1899	78.7 mm (3.1 in)
1900	66.3 mm (2.6 in)
1901	98.5 mm (3.9 in)
1902	75.5 mm (3.0 in)
1903	72.7 mm (2.9 in)
1904	106.9 mm (4.2 in)
1905	76.7 mm (3.0 in)
1906	100.6 mm (4.0 in)
1907	43.2 mm (1.7 in)
1908	72.0 mm (2.8 in)
1909	66.3 mm (2.6 in)
1910	53.1 mm (2.1 in)
1911	74.4 mm (2.9 in)
1912	74.2 mm (2.9 in)
1913	67.4 mm (2.7 in)
1914	48.8 mm (1.9 in)
1915	100.9 mm (4.0 in)
1916	59.5 mm (2.3 in)
1917	68.7 mm (2.7 in)
1918	64.3 mm (2.5 in)
1919	43.9 mm (1.7 in)
1920	64.5 mm (2.5 in)
1921	63.5 mm (2.5 in)
1922	48.3 mm (1.9 in)
1923	52.9 mm (2.1 in)
1924	41.4 mm (1.6 in)
1925	48.1 mm (1.9 in)
1926	113.0 mm (4.4 in)
1927	66.5 mm (2.6 in)
1928	75.4 mm (3.0 in)
1929	82.8 mm (3.3 in)
1930	106.7 mm (4.2 in)
1931	74.2 mm (2.9 in)
1932	59.9 mm (2.4 in)
1933	59.6 mm (2.3 in)
1934	60.3 mm (2.4 in)
1935	106.8 mm (4.2 in)
1947	70.6 mm (2.8 in)
1948	69.1 mm (2.7 in)
1949	74.0 mm (2.9 in)
1950	82.6 mm (3.3 in)
1951	65.9 mm (2.6 in)
1952	65.8 mm (2.6 in)
1953	63.5 mm (2.5 in)
1954	81.3 mm (3.2 in)
1955	55.6 mm (2.2 in)
1959	52.3 mm (2.1 in)
1961	65.3 mm (2.6 in)
1962	82.5 mm (3.2 in)
1963	76.2 mm (3.0 in)
1964	n/a

Longest dry spell (CDD)

The longest dry spell of the year at Alton, 1887 to 1964. The record is 39 days in 1908, marked on the chart; the median year is 17 days.

Longest dry spell (CDD) at Alton by year
Year	Longest dry spell (CDD)
1887	17 days
1888	13 days
1889	21 days
1890	14 days
1891	21 days
1892	14 days
1893	13 days
1894	14 days
1895	13 days
1896	12 days
1897	15 days
1898	17 days
1899	20 days
1900	17 days
1901	17 days
1902	18 days
1903	15 days
1904	13 days
1905	12 days
1906	12 days
1907	14 days
1908	39 days
1909	12 days
1910	15 days
1911	15 days
1912	19 days
1913	13 days
1914	16 days
1915	18 days
1916	24 days
1917	15 days
1918	17 days
1919	12 days
1920	16 days
1921	12 days
1922	17 days
1923	21 days
1924	36 days
1925	15 days
1926	19 days
1927	20 days
1928	15 days
1929	20 days
1930	12 days
1931	11 days
1932	16 days
1933	22 days
1934	18 days
1935	19 days
1947	36 days
1948	17 days
1949	32 days
1950	14 days
1951	22 days
1952	24 days
1953	17 days
1954	23 days
1955	17 days
1959	14 days
1961	16 days
1962	10 days
1963	31 days
1964	n/a

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

49 years with a frost

Across 49 years with a frost, the median last spring frost at Alton falls on 22 May and the median first autumn frost on 21 September, which leaves a median of 123 days between them.

Fitted over all years, the growing season changes by -0.5 days per decade at this station.

Frost dates and growing season at Alton
Measure	Median, all years	Earliest period	Recent period (1906 to 1962)	Recent against earliest	Fitted trend
Last spring frost	22 May	n/a	23 May	n/a	-0.6 days per decade
First autumn frost	21 September	n/a	23 September	n/a	-1.1 days per decade
Growing days	123 days	n/a	123 days	n/a	-0.5 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

49 years, 1887 to 1951

A day with at least 49.0 mm (1.9 in) of rain is expected about once in 2 years. A day with at least 105.8 mm (4.2 in) of rain is expected about once in 100 years.

Rainfall return levels at Alton: the daily rain expected about once in a given number of years
Expected about once in	A day with at least	Note
2 years	49.0 mm (1.9 in)
5 years	62.7 mm (2.5 in)
10 years	72.4 mm (2.9 in)
25 years	85.3 mm (3.4 in)
50 years	95.4 mm (3.8 in)	Longer than the 49 years of record
100 years	105.8 mm (4.2 in)	Longer than the 49 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, 49 years of values from 1887 to 1951.

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: 104.4 mm (4.1 in) in 1904; 87.6 mm (3.4 in) in 1891; 76.5 mm (3.0 in) in 1935.

Station Changes

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

Download the Data

Data for Alton standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Alton 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 2026-10-17. Last revised 17 October 2026 (2026-10-17).