Palo Alto Weather Records (USC00046646)

Record envelope, standing records and threshold days for Palo Alto (USC00046646), California, United States, with 65 years of record.

Key Facts for Palo Alto

Palo Alto (USC00046646) is a weather station in California, United States at 37.44 latitude and -122.14 longitude, 8 m (25 ft) above sea level.
The station reports from 1953 to 2017, 65 years of record.
1,464 records set at Palo Alto still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Palo Alto set a daily record precipitation of 24.9 mm (1.0 in) on 16 November 2017.

About the Station

Location: California, United States, 37.44 latitude, -122.14 longitude.
Elevation: 8 m (25 ft).
Period of record: 1953 to 2017, 65 years.
Eligible elements: tmax, tmin, prcp, snow, snwd.

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 Palo Alto. 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 Palo Alto, with 2026 drawn through them
Month	Highest record high	Lowest record low	2026 highest maximum	2026 lowest minimum
Jan	23.9 C (75.0 F)	-6.1 C (21.0 F)	n/a	n/a
Feb	28.9 C (84.0 F)	-6.7 C (19.9 F)	n/a	n/a
Mar	29.4 C (84.9 F)	-5.6 C (21.9 F)	n/a	n/a
Apr	36.7 C (98.1 F)	-0.6 C (30.9 F)	n/a	n/a
May	37.8 C (100.0 F)	0.6 C (33.1 F)	n/a	n/a
Jun	41.7 C (107.1 F)	4.4 C (39.9 F)	n/a	n/a
Jul	40.6 C (105.1 F)	5.0 C (41.0 F)	n/a	n/a
Aug	38.3 C (100.9 F)	6.7 C (44.1 F)	n/a	n/a
Sep	40.6 C (105.1 F)	2.8 C (37.0 F)	n/a	n/a
Oct	37.8 C (100.0 F)	0.6 C (33.1 F)	n/a	n/a
Nov	31.7 C (89.1 F)	-3.3 C (26.1 F)	n/a	n/a
Dec	23.9 C (75.0 F)	-6.7 C (19.9 F)	n/a	n/a

Which Years Hold Standing Records

1,464 standing records

1,464 records at Palo Alto still stand. 1964 holds the most, with 56.

Standing records at Palo Alto by the year they were set
Year set	Standing records
1953	11
1954	50
1955	51
1956	27
1957	30
1958	44
1959	43
1960	30
1961	37
1962	41
1963	40
1964	56
1965	29
1966	19
1967	26
1968	24
1969	17
1970	17
1971	27
1972	32
1973	27
1974	16
1975	23
1976	40
1977	25
1978	19
1979	11
1980	20
1981	21
1982	38
1983	13
1984	18
1985	18
1986	14
1987	13
1988	17
1989	27
1990	25
1991	18
1992	6
1993	34
1994	35
1995	19
1996	23
1997	18
1998	13
1999	8
2000	3
2001	27
2002	11
2003	12
2004	19
2005	8
2006	20
2007	12
2008	18
2009	14
2010	11
2011	13
2012	21
2013	14
2014	8
2015	16
2016	9
2017	18

All-Time Record Progression

2 new records

2 all-time records were set at Palo Alto between 23 December 1990 and 3 February 1998. Each dot is a new record.

When Palo Alto set new all-time records
Date	Kind	Detail
1990-12-23	Record low minimum temperature	Record low minimum temperature -6.7 C (19.9 F)
1998-02-03	Record daily precipitation	Record daily precipitation 95.3 mm (3.8 in)

Wettest Day of Each Month

Feb: 95.3 mm (3.8 in)

The wettest day on record for each calendar month at Palo Alto. The most was 95.3 mm (3.8 in) on 3 February 1998.

Record daily precipitation for each month at Palo Alto
Month	Record daily precipitation (mm)	Date
Jan	66.0 mm (2.6 in)	5 January 1982
Feb	95.3 mm (3.8 in)	3 February 1998
Mar	49.3 mm (1.9 in)	25 March 2011
Apr	39.4 mm (1.6 in)	3 April 1958
May	25.9 mm (1.0 in)	7 May 1994
Jun	20.8 mm (0.8 in)	16 June 1995
Jul	8.4 mm (0.33 in)	31 July 1966
Aug	14.7 mm (0.6 in)	20 August 1997
Sep	45.2 mm (1.8 in)	19 September 1959
Oct	47.2 mm (1.9 in)	13 October 1962
Nov	63.0 mm (2.5 in)	29 November 1970
Dec	70.4 mm (2.8 in)	22 December 1955

Period of Record Coverage

1953 to 2017

65 years of record at Palo Alto, 1953 to 2017. 20 years have data for under 90 percent of days and are left out of rankings: 1953, 1966, 1967, 1983, 1985, 1987, 1999, 2000 and others.

Days with data per year at Palo Alto
Year	Days with data	Share of year	Complete
1953	122	33%	No
1954	365	100%	Yes
1955	365	100%	Yes
1956	366	100%	Yes
1957	364	100%	Yes
1958	362	99%	Yes
1959	365	100%	Yes
1960	364	99%	Yes
1961	361	99%	Yes
1962	363	99%	Yes
1963	348	95%	Yes
1964	360	98%	Yes
1965	355	97%	Yes
1966	306	84%	No
1967	281	77%	No
1968	366	100%	Yes
1969	364	100%	Yes
1970	365	100%	Yes
1971	364	100%	Yes
1972	366	100%	Yes
1973	363	99%	Yes
1974	360	99%	Yes
1975	353	97%	Yes
1976	364	99%	Yes
1977	334	92%	Yes
1978	348	95%	Yes
1979	348	95%	Yes
1980	348	95%	Yes
1981	359	98%	Yes
1982	360	99%	Yes
1983	294	81%	No
1984	353	96%	Yes
1985	327	90%	No
1986	361	99%	Yes
1987	304	83%	No
1988	365	100%	Yes
1989	360	99%	Yes
1990	334	92%	Yes
1991	360	99%	Yes
1992	365	100%	Yes
1993	331	91%	Yes
1994	358	98%	Yes
1995	365	100%	Yes
1996	356	97%	Yes
1997	361	99%	Yes
1998	346	95%	Yes
1999	226	62%	No
2000	131	36%	No
2001	310	85%	No
2002	287	79%	No
2003	301	82%	No
2004	311	85%	No
2005	344	94%	Yes
2006	336	92%	Yes
2007	331	91%	Yes
2008	316	86%	No
2009	286	78%	No
2010	300	82%	No
2011	323	88%	No
2012	343	94%	Yes
2013	317	87%	No
2014	299	82%	No
2015	313	86%	No
2016	328	90%	No
2017	338	93%	Yes

Latest Records

Latest records at Palo Alto
Date	Station	Record	Value	Beat old record by	Old record stood	Significance
16 November 2017	Palo Alto, US	daily rain	24.9 mm (1.0 in)	0.8 mm (0.03 in)	44 years	19 of 100 (Routine)
25 October 2017	Palo Alto, US	daily high max	31.1 C (88.0 F)	0.5 C (0.9 F)	52 years	22 of 100 (Routine)
20 October 2017	Palo Alto, US	daily low min	2.2 C (36.0 F)	1.1 C (2.0 F)	4 years	10 of 100 (Routine)
12 September 2017	Palo Alto, US	daily rain	3.3 mm (0.13 in)	3.3 mm (0.13 in)	64 years	20 of 100 (Routine)
4 September 2017	Palo Alto, US	daily high min	17.8 C (64.0 F)	1.7 C (3.1 F)	19 years	18 of 100 (Routine)
3 September 2017	Palo Alto, US	daily high max	40.0 C (104.0 F)	5.0 C (9.0 F)	62 years	36 of 100 (Notable)
3 September 2017	Palo Alto, US	daily high min	18.9 C (66.0 F)	1.7 C (3.1 F)	48 years	27 of 100 (Routine)
2 September 2017	Palo Alto, US	monthly high max (Tie)	40.6 C (105.1 F)	tie	45 years	7 of 100 (Routine)
17 August 2017	Palo Alto, US	daily low min	8.9 C (48.0 F)	0.5 C (0.9 F)	60 years	26 of 100 (Routine)
5 August 2017	Palo Alto, US	daily high min (Tie)	16.1 C (61.0 F)	tie	43 years	4 of 100 (Routine)
24 July 2017	Palo Alto, US	daily low min	8.3 C (46.9 F)	1.1 C (2.0 F)	54 years	27 of 100 (Routine)
22 July 2017	Palo Alto, US	daily low min	7.8 C (46.0 F)	1.6 C (2.9 F)	52 years	28 of 100 (Routine)
21 July 2017	Palo Alto, US	daily low min (Tie)	9.4 C (48.9 F)	tie	54 years	5 of 100 (Routine)
17 July 2017	Palo Alto, US	daily high max	35.6 C (96.1 F)	1.7 C (3.1 F)	14 years	14 of 100 (Routine)
8 July 2017	Palo Alto, US	daily high max	33.9 C (93.0 F)	0.6 C (1.1 F)	15 years	11 of 100 (Routine)
19 June 2017	Palo Alto, US	daily high min	17.2 C (63.0 F)	1.6 C (2.9 F)	48 years	26 of 100 (Routine)
19 June 2017	Palo Alto, US	daily high max	38.3 C (100.9 F)	2.7 C (4.9 F)	36 years	22 of 100 (Routine)
18 June 2017	Palo Alto, US	daily high min	17.8 C (64.0 F)	2.2 C (4.0 F)	48 years	29 of 100 (Routine)
5 May 2017	Palo Alto, US	daily high max	32.8 C (91.0 F)	2.2 C (4.0 F)	60 years	29 of 100 (Routine)
4 May 2017	Palo Alto, US	daily high max	33.3 C (91.9 F)	1.6 C (2.9 F)	4 years	10 of 100 (Routine)

Climate Trend

42 complete years, 1954 to 2017

One stripe for each of 42 complete years at Palo Alto, 1954 to 2017. Blue stripes are years cooler than the station's own mean of 14.5 C (58.0 F); red stripes are warmer. The coolest year was 1994, at 12.6 C (54.7 F), and the warmest was 1997, at 15.8 C (60.5 F). The strongest colour marks a difference of 1.9 C (3.4 F).

Annual mean temperature at Palo Alto as warming stripes, 1954 to 2017
Year	Annual mean temperature	Difference from the station mean
1954	14.4 C	-0.05 C
1955	14.0 C	-0.43 C
1956	14.5 C	+0.00 C
1957	14.9 C	+0.39 C
1958	15.4 C	+0.96 C
1959	15.0 C	+0.49 C
1960	14.2 C	-0.24 C
1961	14.2 C	-0.24 C
1962	13.7 C	-0.75 C
1963	13.8 C	-0.65 C
1964	13.4 C	-1.07 C
1965	13.5 C	-0.93 C
1968	14.9 C	+0.42 C
1969	14.5 C	+0.05 C
1970	14.6 C	+0.14 C
1971	14.0 C	-0.51 C
1972	14.3 C	-0.14 C
1973	14.4 C	-0.07 C
1974	14.2 C	-0.29 C
1975	14.2 C	-0.23 C
1976	14.6 C	+0.13 C
1979	14.7 C	+0.20 C
1980	14.2 C	-0.24 C
1981	15.0 C	+0.50 C
1982	13.5 C	-0.93 C
1984	14.8 C	+0.36 C
1986	14.8 C	+0.30 C
1988	14.8 C	+0.33 C
1989	14.3 C	-0.13 C
1991	13.9 C	-0.60 C
1992	14.6 C	+0.10 C
1994	12.6 C	-1.88 C
1995	15.5 C	+1.05 C
1996	15.8 C	+1.31 C
1997	15.8 C	+1.37 C
1998	14.6 C	+0.10 C
2005	14.7 C	+0.26 C
2006	14.4 C	-0.08 C
2007	14.2 C	-0.24 C
2012	14.3 C	-0.18 C
2016	15.2 C	+0.73 C
2017	15.1 C	+0.63 C

The fitted trend in annual mean temperature here over 1954 to 2017 is 0.09 C (-0.02 to 0.19) per decade. The interval includes zero, so the trend is not clearly different from zero. In Fahrenheit: 0.15 F (-0.04 to 0.35) per decade. The slope is a straight line fitted to 42 complete years; the brackets give its 95 percent interval.

Fitted temperature trends per decade at Palo Alto
Measure	Per decade (C)	Per decade (F)	Period	Complete years	Reading
Annual mean temperature	0.09 C (-0.02 to 0.19) per decade	0.15 F (-0.04 to 0.35) per decade	1954 to 2017	42	Not clearly different from zero
Mean daily maximum	0.09 C (-0.05 to 0.23) per decade	0.2 F (-0.1 to 0.4) per decade	1954 to 2017	42	Not clearly different from zero
Mean daily minimum	0.08 C (-0.04 to 0.20) per decade	0.1 F (-0.1 to 0.4) per decade	1954 to 2017	42	Not clearly different from zero

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

1953 to 2017

Yearly extremes at Palo Alto: the record and the median year
Measure	Record	Year of the record	Median year	Years with a value
Hottest day (TXx)	41.7 C (107.1 F)	1961	36.7 C (98.1 F)	65
Coldest night (TNn)	-6.7 C (19.9 F)	1990	-2.8 C (27.0 F)	65
Wettest day (Rx1day)	95.3 mm (3.8 in)	1998	39.4 mm (1.6 in)	65
Wettest five days (Rx5day)	152.9 mm (6.0 in)	1955	68.3 mm (2.7 in)	65
Longest dry spell (CDD)	200 days	1965	108 days	65

Hottest day (TXx)

The hottest day of the year at Palo Alto, 1953 to 2017. The record is 41.7 C (107.1 F) in 1961, marked on the chart; the median year is 36.7 C (98.1 F).

Hottest day (TXx) at Palo Alto by year
Year	Hottest day (TXx)
1953	36.7 C (98.1 F)
1954	38.3 C (100.9 F)
1955	36.1 C (97.0 F)
1956	37.2 C (99.0 F)
1957	37.8 C (100.0 F)
1958	37.8 C (100.0 F)
1959	38.3 C (100.9 F)
1960	41.1 C (106.0 F)
1961	41.7 C (107.1 F)
1962	35.6 C (96.1 F)
1963	35.6 C (96.1 F)
1964	35.0 C (95.0 F)
1965	32.8 C (91.0 F)
1966	37.8 C (100.0 F)
1967	35.0 C (95.0 F)
1968	38.3 C (100.9 F)
1969	32.8 C (91.0 F)
1970	38.3 C (100.9 F)
1971	40.6 C (105.1 F)
1972	40.6 C (105.1 F)
1973	39.4 C (102.9 F)
1974	35.0 C (95.0 F)
1975	35.0 C (95.0 F)
1976	41.1 C (106.0 F)
1977	38.3 C (100.9 F)
1978	35.6 C (96.1 F)
1979	39.4 C (102.9 F)
1980	37.8 C (100.0 F)
1981	38.9 C (102.0 F)
1982	36.1 C (97.0 F)
1983	37.2 C (99.0 F)
1984	36.7 C (98.1 F)
1985	36.1 C (97.0 F)
1986	35.0 C (95.0 F)
1987	36.7 C (98.1 F)
1988	40.6 C (105.1 F)
1989	36.7 C (98.1 F)
1990	36.7 C (98.1 F)
1991	33.9 C (93.0 F)
1992	31.7 C (89.1 F)
1993	36.7 C (98.1 F)
1994	32.8 C (91.0 F)
1995	38.9 C (102.0 F)
1996	37.2 C (99.0 F)
1997	37.8 C (100.0 F)
1998	37.8 C (100.0 F)
1999	32.8 C (91.0 F)
2000	28.3 C (82.9 F)
2001	37.2 C (99.0 F)
2002	38.3 C (100.9 F)
2003	37.2 C (99.0 F)
2004	36.1 C (97.0 F)
2005	34.4 C (93.9 F)
2006	37.2 C (99.0 F)
2007	34.4 C (93.9 F)
2008	37.8 C (100.0 F)
2009	37.2 C (99.0 F)
2010	37.8 C (100.0 F)
2011	36.1 C (97.0 F)
2012	36.7 C (98.1 F)
2013	34.4 C (93.9 F)
2014	34.4 C (93.9 F)
2015	36.7 C (98.1 F)
2016	34.4 C (93.9 F)
2017	40.6 C (105.1 F)

Coldest night (TNn)

The coldest night of the year at Palo Alto, 1953 to 2017. The record is -6.7 C (19.9 F) in 1990, marked on the chart; the median year is -2.8 C (27.0 F).

Coldest night (TNn) at Palo Alto by year
Year	Coldest night (TNn)
1953	-1.1 C (30.0 F)
1954	-2.8 C (27.0 F)
1955	-2.8 C (27.0 F)
1956	-2.8 C (27.0 F)
1957	-2.2 C (28.0 F)
1958	-2.2 C (28.0 F)
1959	-1.7 C (28.9 F)
1960	-5.6 C (21.9 F)
1961	-3.9 C (25.0 F)
1962	-4.4 C (24.1 F)
1963	-6.1 C (21.0 F)
1964	-2.2 C (28.0 F)
1965	-4.4 C (24.1 F)
1966	-3.3 C (26.1 F)
1967	-3.3 C (26.1 F)
1968	-3.9 C (25.0 F)
1969	-1.7 C (28.9 F)
1970	-3.3 C (26.1 F)
1971	-1.7 C (28.9 F)
1972	-5.0 C (23.0 F)
1973	-2.8 C (27.0 F)
1974	-3.3 C (26.1 F)
1975	-3.3 C (26.1 F)
1976	-4.4 C (24.1 F)
1977	-1.7 C (28.9 F)
1978	-3.9 C (25.0 F)
1979	-3.3 C (26.1 F)
1980	-2.8 C (27.0 F)
1981	0.6 C (33.1 F)
1982	-3.9 C (25.0 F)
1983	-2.2 C (28.0 F)
1984	-1.1 C (30.0 F)
1985	-2.8 C (27.0 F)
1986	0.6 C (33.1 F)
1987	-1.7 C (28.9 F)
1988	-2.2 C (28.0 F)
1989	-3.3 C (26.1 F)
1990	-6.7 C (19.9 F)
1991	-2.8 C (27.0 F)
1992	-2.2 C (28.0 F)
1993	-3.9 C (25.0 F)
1994	-2.2 C (28.0 F)
1995	0.6 C (33.1 F)
1996	-0.6 C (30.9 F)
1997	-2.8 C (27.0 F)
1998	-6.1 C (21.0 F)
1999	0.0 C (32.0 F)
2000	0.6 C (33.1 F)
2001	-2.2 C (28.0 F)
2002	-2.2 C (28.0 F)
2003	-0.6 C (30.9 F)
2004	-5.6 C (21.9 F)
2005	-0.6 C (30.9 F)
2006	-2.2 C (28.0 F)
2007	-3.9 C (25.0 F)
2008	-1.1 C (30.0 F)
2009	-2.8 C (27.0 F)
2010	-1.1 C (30.0 F)
2011	-2.2 C (28.0 F)
2012	-2.8 C (27.0 F)
2013	-6.7 C (19.9 F)
2014	-2.2 C (28.0 F)
2015	-2.8 C (27.0 F)
2016	-2.2 C (28.0 F)
2017	-1.1 C (30.0 F)

Wettest day (Rx1day)

The wettest day of the year at Palo Alto, 1953 to 2017. The record is 95.3 mm (3.8 in) in 1998, marked on the chart; the median year is 39.4 mm (1.6 in).

Wettest day (Rx1day) at Palo Alto by year
Year	Wettest day (Rx1day)
1953	35.6 mm (1.4 in)
1954	24.6 mm (1.0 in)
1955	70.4 mm (2.8 in)
1956	23.4 mm (0.9 in)
1957	32.5 mm (1.3 in)
1958	39.4 mm (1.6 in)
1959	45.2 mm (1.8 in)
1960	35.6 mm (1.4 in)
1961	43.2 mm (1.7 in)
1962	47.2 mm (1.9 in)
1963	44.2 mm (1.7 in)
1964	43.2 mm (1.7 in)
1965	34.0 mm (1.3 in)
1966	30.2 mm (1.2 in)
1967	47.2 mm (1.9 in)
1968	36.3 mm (1.4 in)
1969	46.2 mm (1.8 in)
1970	63.0 mm (2.5 in)
1971	29.0 mm (1.1 in)
1972	39.4 mm (1.6 in)
1973	47.8 mm (1.9 in)
1974	46.2 mm (1.8 in)
1975	26.4 mm (1.0 in)
1976	16.3 mm (0.6 in)
1977	32.8 mm (1.3 in)
1978	28.4 mm (1.1 in)
1979	35.1 mm (1.4 in)
1980	35.6 mm (1.4 in)
1981	47.8 mm (1.9 in)
1982	66.0 mm (2.6 in)
1983	45.5 mm (1.8 in)
1984	29.2 mm (1.1 in)
1985	22.6 mm (0.9 in)
1986	47.8 mm (1.9 in)
1987	19.3 mm (0.8 in)
1988	39.6 mm (1.6 in)
1989	21.8 mm (0.9 in)
1990	20.3 mm (0.8 in)
1991	35.3 mm (1.4 in)
1992	46.5 mm (1.8 in)
1993	38.1 mm (1.5 in)
1994	25.9 mm (1.0 in)
1995	51.3 mm (2.0 in)
1996	35.8 mm (1.4 in)
1997	45.2 mm (1.8 in)
1998	95.3 mm (3.8 in)
1999	27.2 mm (1.1 in)
2000	42.4 mm (1.7 in)
2001	25.9 mm (1.0 in)
2002	41.9 mm (1.6 in)
2003	40.6 mm (1.6 in)
2004	42.4 mm (1.7 in)
2005	39.9 mm (1.6 in)
2006	38.1 mm (1.5 in)
2007	13.0 mm (0.5 in)
2008	47.0 mm (1.9 in)
2009	43.9 mm (1.7 in)
2010	37.6 mm (1.5 in)
2011	49.3 mm (1.9 in)
2012	45.7 mm (1.8 in)
2013	20.1 mm (0.8 in)
2014	54.9 mm (2.2 in)
2015	40.1 mm (1.6 in)
2016	36.8 mm (1.4 in)
2017	33.3 mm (1.3 in)

Wettest five days (Rx5day)

The wettest five days of the year at Palo Alto, 1953 to 2017. The record is 152.9 mm (6.0 in) in 1955, marked on the chart; the median year is 68.3 mm (2.7 in).

Wettest five days (Rx5day) at Palo Alto by year
Year	Wettest five days (Rx5day)
1953	43.3 mm (1.7 in)
1954	46.6 mm (1.8 in)
1955	152.9 mm (6.0 in)
1956	23.7 mm (0.9 in)
1957	57.9 mm (2.3 in)
1958	91.2 mm (3.6 in)
1959	68.5 mm (2.7 in)
1960	38.0 mm (1.5 in)
1961	43.2 mm (1.7 in)
1962	84.1 mm (3.3 in)
1963	92.4 mm (3.6 in)
1964	72.9 mm (2.9 in)
1965	63.2 mm (2.5 in)
1966	65.5 mm (2.6 in)
1967	54.1 mm (2.1 in)
1968	70.8 mm (2.8 in)
1969	82.6 mm (3.3 in)
1970	144.6 mm (5.7 in)
1971	56.6 mm (2.2 in)
1972	92.5 mm (3.6 in)
1973	70.3 mm (2.8 in)
1974	61.5 mm (2.4 in)
1975	48.6 mm (1.9 in)
1976	30.7 mm (1.2 in)
1977	45.8 mm (1.8 in)
1978	90.6 mm (3.6 in)
1979	58.6 mm (2.3 in)
1980	95.3 mm (3.8 in)
1981	68.3 mm (2.7 in)
1982	104.8 mm (4.1 in)
1983	109.2 mm (4.3 in)
1984	40.2 mm (1.6 in)
1985	48.4 mm (1.9 in)
1986	136.2 mm (5.4 in)
1987	41.3 mm (1.6 in)
1988	58.2 mm (2.3 in)
1989	30.7 mm (1.2 in)
1990	35.5 mm (1.4 in)
1991	64.3 mm (2.5 in)
1992	93.7 mm (3.7 in)
1993	67.9 mm (2.7 in)
1994	48.5 mm (1.9 in)
1995	92.5 mm (3.6 in)
1996	56.6 mm (2.2 in)
1997	77.8 mm (3.1 in)
1998	140.2 mm (5.5 in)
1999	56.7 mm (2.2 in)
2000	85.1 mm (3.4 in)
2001	79.0 mm (3.1 in)
2002	120.9 mm (4.8 in)
2003	47.2 mm (1.9 in)
2004	87.6 mm (3.4 in)
2005	72.2 mm (2.8 in)
2006	91.4 mm (3.6 in)
2007	33.6 mm (1.3 in)
2008	72.7 mm (2.9 in)
2009	43.9 mm (1.7 in)
2010	75.0 mm (3.0 in)
2011	95.5 mm (3.8 in)
2012	66.2 mm (2.6 in)
2013	29.8 mm (1.2 in)
2014	91.5 mm (3.6 in)
2015	75.1 mm (3.0 in)
2016	52.3 mm (2.1 in)
2017	73.6 mm (2.9 in)

Longest dry spell (CDD)

The longest dry spell of the year at Palo Alto, 1953 to 2017. The record is 200 days in 1965, marked on the chart; the median year is 108 days.

Longest dry spell (CDD) at Palo Alto by year
Year	Longest dry spell (CDD)
1953	39 days
1954	144 days
1955	189 days
1956	132 days
1957	129 days
1958	105 days
1959	177 days
1960	185 days
1961	107 days
1962	165 days
1963	124 days
1964	83 days
1965	200 days
1966	53 days
1967	121 days
1968	91 days
1969	173 days
1970	132 days
1971	149 days
1972	108 days
1973	177 days
1974	84 days
1975	80 days
1976	65 days
1977	117 days
1978	136 days
1979	88 days
1980	142 days
1981	127 days
1982	75 days
1983	104 days
1984	133 days
1985	98 days
1986	135 days
1987	175 days
1988	128 days
1989	116 days
1990	67 days
1991	90 days
1992	77 days
1993	56 days
1994	115 days
1995	170 days
1996	165 days
1997	76 days
1998	130 days
1999	52 days
2000	15 days
2001	88 days
2002	71 days
2003	176 days
2004	108 days
2005	119 days
2006	50 days
2007	89 days
2008	102 days
2009	91 days
2010	111 days
2011	33 days
2012	50 days
2013	64 days
2014	48 days
2015	36 days
2016	40 days
2017	147 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

36 years with a frost

Across 36 years with a frost, the median last spring frost at Palo Alto falls on 10 February and the median first autumn frost on 1 December, which leaves a median of 298 days between them.

Fitted over all years, the growing season changes by +3.9 days per decade at this station.

Frost dates and growing season at Palo Alto
Measure	Median, all years	Earliest period	Recent period (1960 to 2017)	Recent against earliest	Fitted trend
Last spring frost	10 February	n/a	7 February	n/a	-3.4 days per decade
First autumn frost	1 December	n/a	2 December	n/a	+0.5 days per decade
Growing days	298 days	n/a	296 days	n/a	+3.9 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

55 years, 1954 to 2017

A day with at least 38.1 mm (1.5 in) of rain is expected about once in 2 years. A day with at least 74.2 mm (2.9 in) of rain is expected about once in 100 years.

Rainfall return levels at Palo Alto: the daily rain expected about once in a given number of years
Expected about once in	A day with at least	Note
2 years	38.1 mm (1.5 in)
5 years	49.6 mm (2.0 in)
10 years	56.4 mm (2.2 in)
25 years	64.2 mm (2.5 in)
50 years	69.4 mm (2.7 in)
100 years	74.2 mm (2.9 in)	Longer than the 55 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, 55 years of values from 1954 to 2017.

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: 95.3 mm (3.8 in) in 1998; 70.4 mm (2.8 in) in 1955; 66.0 mm (2.6 in) in 1982.

Station Changes

1 suspected

One change was suspected in the annual mean temperature of Palo Alto, at 2005. Each is measured against neighbouring stations.

Relative to 5 neighbouring stations, the station's annual mean temperature from 2005 ran 0.4 C (0.7 F) lower than in the years before (possible change).

Suspected changes in the annual mean temperature at Palo Alto, against neighbouring stations
Year	Shift (C)	Shift (F)	Strength	Neighbours
2005	-0.4	-0.7	possible	5

Possible change at the station (a move, a new instrument or a new site); the record is kept as measured. A "likely" change has a larger test statistic than a "possible" one. Neither says why the station differs from its neighbours. How changes are found, and the largest ones.

Download the Data

Data for Palo Alto standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Palo Alto 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 2025-12-31. Last revised 31 December 2025 (2025-12-31).