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
Record highRecord low2026 daily maximum2026 daily minimum
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
Year with most
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
Complete yearUnder 90 percent of days
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.
Cooler than the station meanWarmer than the station mean
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 2026-10-14 (14 October 2026). Records are computed by this site and are not official.