Hamilton Af Base Weather Records (USW00023211)

Record envelope, standing records and threshold days for Hamilton Af Base (USW00023211), California, United States, with 37 years of record.

Key Facts for Hamilton Af Base

Hamilton Af Base (USW00023211) is a weather station in California, United States at 38.07 latitude and -122.52 longitude, 4 m (13 ft) above sea level.
The station reports from 1934 to 1970, 37 years of record.
1,464 records set at Hamilton Af Base still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Hamilton Af Base tied a daily record low minimum temperature of -1.7 C (28.9 F) on 24 December 1970.

About the Station

Location: California, United States, 38.07 latitude, -122.52 longitude.
Elevation: 4 m (13 ft).
Period of record: 1934 to 1970, 37 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 Hamilton Af Base. 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 Hamilton Af Base, with 2026 drawn through them
Month	Highest record high	Lowest record low	2026 highest maximum	2026 lowest minimum
Jan	25.0 C (77.0 F)	-5.0 C (23.0 F)	n/a	n/a
Feb	25.0 C (77.0 F)	-6.7 C (19.9 F)	n/a	n/a
Mar	30.6 C (87.1 F)	-2.2 C (28.0 F)	n/a	n/a
Apr	31.7 C (89.1 F)	-1.1 C (30.0 F)	n/a	n/a
May	38.9 C (102.0 F)	2.2 C (36.0 F)	n/a	n/a
Jun	41.1 C (106.0 F)	5.0 C (41.0 F)	n/a	n/a
Jul	38.9 C (102.0 F)	6.1 C (43.0 F)	n/a	n/a
Aug	38.9 C (102.0 F)	6.7 C (44.1 F)	n/a	n/a
Sep	41.7 C (107.1 F)	3.3 C (37.9 F)	n/a	n/a
Oct	35.6 C (96.1 F)	-1.1 C (30.0 F)	n/a	n/a
Nov	28.3 C (82.9 F)	-3.3 C (26.1 F)	n/a	n/a
Dec	24.4 C (75.9 F)	-5.0 C (23.0 F)	n/a	n/a

Which Years Hold Standing Records

1,464 standing records

1,464 records at Hamilton Af Base still stand. 1939 holds the most, with 71.

Standing records at Hamilton Af Base by the year they were set
Year set	Standing records
1934	53
1935	61
1936	5
1937	1
1938	17
1939	71
1940	47
1941	40
1942	31
1943	47
1944	34
1945	36
1946	26
1947	38
1948	50
1949	48
1950	50
1951	36
1952	39
1953	39
1954	49
1955	37
1956	22
1957	39
1958	45
1959	45
1960	32
1961	50
1962	35
1963	55
1964	52
1965	50
1966	35
1967	51
1968	30
1969	33
1970	35

All-Time Record Progression

1 new records

1 all-time records were set at Hamilton Af Base between 21 January 1967 and 21 January 1967. Each dot is a new record.

Wettest Day of Each Month

Jan: 100.1 mm (3.9 in)

The wettest day on record for each calendar month at Hamilton Af Base. The most was 100.1 mm (3.9 in) on 21 January 1967.

Record daily precipitation for each month at Hamilton Af Base
Month	Record daily precipitation (mm)	Date
Jan	100.1 mm (3.9 in)	21 January 1967
Feb	81.0 mm (3.2 in)	9 February 1962
Mar	59.2 mm (2.3 in)	14 March 1952
Apr	58.2 mm (2.3 in)	4 April 1941
May	20.8 mm (0.8 in)	30 May 1940
Jun	46.0 mm (1.8 in)	8 June 1964
Jul	0.8 mm (0.03 in)	25 July 1946
Aug	17.0 mm (0.7 in)	11 August 1965
Sep	57.9 mm (2.3 in)	18 September 1959
Oct	98.8 mm (3.9 in)	12 October 1962
Nov	89.9 mm (3.5 in)	27 November 1970
Dec	98.3 mm (3.9 in)	3 December 1950

Period of Record Coverage

1934 to 1970

37 years of record at Hamilton Af Base, 1934 to 1970. 6 years have data for under 90 percent of days and are left out of rankings: 1936, 1937, 1938, 1946, 1947, 1948.

Days with data per year at Hamilton Af Base
Year	Days with data	Share of year	Complete
1934	329	90%	Yes
1935	360	99%	Yes
1936	61	17%	No
1937	30	8%	No
1938	150	41%	No
1939	364	100%	Yes
1940	364	99%	Yes
1941	359	98%	Yes
1942	365	100%	Yes
1943	364	100%	Yes
1944	366	100%	Yes
1945	357	98%	Yes
1946	314	86%	No
1947	313	86%	No
1948	307	84%	No
1949	365	100%	Yes
1950	365	100%	Yes
1951	365	100%	Yes
1952	366	100%	Yes
1953	364	100%	Yes
1954	365	100%	Yes
1955	365	100%	Yes
1956	366	100%	Yes
1957	364	100%	Yes
1958	363	99%	Yes
1959	365	100%	Yes
1960	366	100%	Yes
1961	365	100%	Yes
1962	365	100%	Yes
1963	360	99%	Yes
1964	366	100%	Yes
1965	365	100%	Yes
1966	365	100%	Yes
1967	365	100%	Yes
1968	366	100%	Yes
1969	365	100%	Yes
1970	365	100%	Yes

Latest Records

Latest records at Hamilton Af Base
Date	Station	Record	Value	Beat old record by	Old record stood	Significance
24 December 1970	Hamilton Af Base, US	daily low min (Tie)	-1.7 C (28.9 F)	tie	21 years	2 of 100 (Routine)
6 December 1970	Hamilton Af Base, US	daily high min	11.1 C (52.0 F)	0.5 C (0.9 F)	15 years	8 of 100 (Routine)
4 December 1970	Hamilton Af Base, US	daily high min	11.7 C (53.1 F)	1.1 C (2.0 F)	24 years	13 of 100 (Routine)
27 November 1970	Hamilton Af Base, US	monthly rain	89.9 mm (3.5 in)	5.8 mm (0.23 in)	16 years	21 of 100 (Routine)
25 November 1970	Hamilton Af Base, US	daily high min (Tie)	12.2 C (54.0 F)	tie	16 years	2 of 100 (Routine)
8 November 1970	Hamilton Af Base, US	daily high min	13.9 C (57.0 F)	1.1 C (2.0 F)	16 years	10 of 100 (Routine)
6 November 1970	Hamilton Af Base, US	daily rain	39.6 mm (1.6 in)	8.4 mm (0.33 in)	29 years	17 of 100 (Routine)
6 November 1970	Hamilton Af Base, US	daily high min (Tie)	11.1 C (52.0 F)	tie	29 years	2 of 100 (Routine)
5 November 1970	Hamilton Af Base, US	daily high min	13.9 C (57.0 F)	1.1 C (2.0 F)	8 years	8 of 100 (Routine)
3 November 1970	Hamilton Af Base, US	daily rain	28.7 mm (1.1 in)	14.5 mm (0.6 in)	28 years	21 of 100 (Routine)
27 October 1970	Hamilton Af Base, US	daily low min	0.6 C (33.1 F)	2.7 C (4.9 F)	29 years	21 of 100 (Routine)
21 October 1970	Hamilton Af Base, US	daily rain	8.4 mm (0.33 in)	0.5 mm (0.02 in)	25 years	10 of 100 (Routine)
20 October 1970	Hamilton Af Base, US	daily rain	18.8 mm (0.7 in)	16.3 mm (0.6 in)	28 years	20 of 100 (Routine)
15 October 1970	Hamilton Af Base, US	daily low max	16.1 C (61.0 F)	0.6 C (1.1 F)	0 years	4 of 100 (Routine)
12 October 1970	Hamilton Af Base, US	daily low max (Tie)	17.8 C (64.0 F)	tie	12 years	1 of 100 (Routine)
3 October 1970	Hamilton Af Base, US	daily low max	18.9 C (66.0 F)	0.5 C (0.9 F)	12 years	7 of 100 (Routine)
30 September 1970	Hamilton Af Base, US	daily high max	34.4 C (93.9 F)	1.1 C (2.0 F)	36 years	15 of 100 (Routine)
17 September 1970	Hamilton Af Base, US	daily low min	6.7 C (44.1 F)	1.1 C (2.0 F)	36 years	17 of 100 (Routine)
16 September 1970	Hamilton Af Base, US	daily low min (Tie)	7.2 C (45.0 F)	tie	25 years	2 of 100 (Routine)
15 September 1970	Hamilton Af Base, US	daily low min	4.4 C (39.9 F)	1.7 C (3.1 F)	31 years	18 of 100 (Routine)

Climate Trend

31 complete years, 1939 to 1970

One stripe for each of 31 complete years at Hamilton Af Base, 1939 to 1970. Blue stripes are years cooler than the station's own mean of 13.9 C (57.0 F); red stripes are warmer. The coolest year was 1965, at 12.6 C (54.7 F), and the warmest was 1959, at 15.0 C (59.0 F). The strongest colour marks a difference of 1.3 C (2.3 F).

Annual mean temperature at Hamilton Af Base as warming stripes, 1939 to 1970
Year	Annual mean temperature	Difference from the station mean
1939	14.5 C	+0.63 C
1940	14.4 C	+0.57 C
1941	14.4 C	+0.55 C
1942	13.6 C	-0.30 C
1943	14.4 C	+0.55 C
1944	13.6 C	-0.22 C
1945	14.3 C	+0.41 C
1946	14.0 C	+0.10 C
1947	14.4 C	+0.58 C
1949	13.6 C	-0.24 C
1950	14.4 C	+0.54 C
1951	13.8 C	-0.10 C
1952	14.0 C	+0.14 C
1953	14.3 C	+0.39 C
1954	13.8 C	-0.02 C
1955	13.7 C	-0.15 C
1956	13.9 C	+0.05 C
1957	14.5 C	+0.62 C
1958	14.8 C	+0.96 C
1959	15.0 C	+1.14 C
1960	13.9 C	+0.08 C
1961	13.4 C	-0.45 C
1962	13.2 C	-0.65 C
1963	13.7 C	-0.20 C
1964	12.8 C	-1.08 C
1965	12.6 C	-1.23 C
1966	13.5 C	-0.39 C
1967	12.9 C	-0.92 C
1968	13.4 C	-0.44 C
1969	13.3 C	-0.53 C
1970	13.6 C	-0.31 C

The annual mean temperature here has fallen by 0.3 C (0.2 to 0.5) per decade over 1939 to 1970. In Fahrenheit: 0.6 F (0.3 to 1.0) per decade. The slope is a straight line fitted to 31 complete years; the brackets give its 95 percent interval.

Fitted temperature trends per decade at Hamilton Af Base
Measure	Per decade (C)	Per decade (F)	Period	Complete years	Reading
Annual mean temperature	-0.3 C (-0.5 to -0.2) per decade	-0.6 F (-1.0 to -0.3) per decade	1939 to 1970	31	Fall
Mean daily maximum	-0.7 C (-0.9 to -0.4) per decade	-1.2 F (-1.7 to -0.8) per decade	1939 to 1970	31	Fall
Mean daily minimum	-0.01 C (-0.26 to 0.23) per decade	-0.03 F (-0.47 to 0.42) per decade	1939 to 1970	31	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

1934 to 1970

Yearly extremes at Hamilton Af Base: 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)	1944	37.2 C (99.0 F)	37
Coldest night (TNn)	-6.7 C (19.9 F)	1948	-2.8 C (27.0 F)	37
Wettest day (Rx1day)	100.1 mm (3.9 in)	1967	64.3 mm (2.5 in)	37
Wettest five days (Rx5day)	294.4 mm (11.6 in)	1955	126.4 mm (5.0 in)	37
Longest dry spell (CDD)	174 days	1943	129 days	37

Hottest day (TXx)

The hottest day of the year at Hamilton Af Base, 1934 to 1970. The record is 41.7 C (107.1 F) in 1944, marked on the chart; the median year is 37.2 C (99.0 F).

Hottest day (TXx) at Hamilton Af Base by year
Year	Hottest day (TXx)
1934	40.0 C (104.0 F)
1935	36.7 C (98.1 F)
1936	38.3 C (100.9 F)
1937	28.9 C (84.0 F)
1938	35.6 C (96.1 F)
1939	38.9 C (102.0 F)
1940	37.2 C (99.0 F)
1941	36.7 C (98.1 F)
1942	35.6 C (96.1 F)
1943	38.9 C (102.0 F)
1944	41.7 C (107.1 F)
1945	37.2 C (99.0 F)
1946	38.9 C (102.0 F)
1947	38.3 C (100.9 F)
1948	38.9 C (102.0 F)
1949	38.3 C (100.9 F)
1950	40.0 C (104.0 F)
1951	37.2 C (99.0 F)
1952	36.7 C (98.1 F)
1953	36.1 C (97.0 F)
1954	38.9 C (102.0 F)
1955	37.8 C (100.0 F)
1956	36.1 C (97.0 F)
1957	36.1 C (97.0 F)
1958	34.4 C (93.9 F)
1959	38.3 C (100.9 F)
1960	40.6 C (105.1 F)
1961	41.1 C (106.0 F)
1962	35.0 C (95.0 F)
1963	35.6 C (96.1 F)
1964	36.7 C (98.1 F)
1965	31.7 C (89.1 F)
1966	37.2 C (99.0 F)
1967	33.9 C (93.0 F)
1968	35.0 C (95.0 F)
1969	35.0 C (95.0 F)
1970	36.7 C (98.1 F)

Coldest night (TNn)

The coldest night of the year at Hamilton Af Base, 1934 to 1970. The record is -6.7 C (19.9 F) in 1948, marked on the chart; the median year is -2.8 C (27.0 F).

Coldest night (TNn) at Hamilton Af Base by year
Year	Coldest night (TNn)
1934	-0.6 C (30.9 F)
1935	-1.7 C (28.9 F)
1936	8.3 C (46.9 F)
1937	3.3 C (37.9 F)
1938	0.0 C (32.0 F)
1939	-1.7 C (28.9 F)
1940	-3.3 C (26.1 F)
1941	-2.2 C (28.0 F)
1942	-2.8 C (27.0 F)
1943	-3.3 C (26.1 F)
1944	-3.9 C (25.0 F)
1945	-2.2 C (28.0 F)
1946	-2.8 C (27.0 F)
1947	-3.9 C (25.0 F)
1948	-6.7 C (19.9 F)
1949	-4.4 C (24.1 F)
1950	-3.9 C (25.0 F)
1951	-1.7 C (28.9 F)
1952	-2.8 C (27.0 F)
1953	-1.1 C (30.0 F)
1954	-1.1 C (30.0 F)
1955	-1.1 C (30.0 F)
1956	-1.7 C (28.9 F)
1957	-2.8 C (27.0 F)
1958	-1.7 C (28.9 F)
1959	-2.2 C (28.0 F)
1960	-3.9 C (25.0 F)
1961	-2.8 C (27.0 F)
1962	-4.4 C (24.1 F)
1963	-5.0 C (23.0 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	-5.0 C (23.0 F)
1969	-3.3 C (26.1 F)
1970	-2.8 C (27.0 F)

Wettest day (Rx1day)

The wettest day of the year at Hamilton Af Base, 1934 to 1970. The record is 100.1 mm (3.9 in) in 1967, marked on the chart; the median year is 64.3 mm (2.5 in).

Wettest day (Rx1day) at Hamilton Af Base by year
Year	Wettest day (Rx1day)
1934	49.8 mm (2.0 in)
1935	43.2 mm (1.7 in)
1936	0.0 mm (0.00 in)
1937	9.4 mm (0.37 in)
1938	73.4 mm (2.9 in)
1939	30.5 mm (1.2 in)
1940	80.0 mm (3.1 in)
1941	58.2 mm (2.3 in)
1942	64.8 mm (2.6 in)
1943	91.2 mm (3.6 in)
1944	43.7 mm (1.7 in)
1945	76.7 mm (3.0 in)
1946	50.3 mm (2.0 in)
1947	37.1 mm (1.5 in)
1948	43.2 mm (1.7 in)
1949	48.8 mm (1.9 in)
1950	98.3 mm (3.9 in)
1951	51.6 mm (2.0 in)
1952	63.8 mm (2.5 in)
1953	62.0 mm (2.4 in)
1954	84.1 mm (3.3 in)
1955	85.6 mm (3.4 in)
1956	48.0 mm (1.9 in)
1957	64.3 mm (2.5 in)
1958	75.2 mm (3.0 in)
1959	69.9 mm (2.8 in)
1960	67.1 mm (2.6 in)
1961	40.9 mm (1.6 in)
1962	98.8 mm (3.9 in)
1963	85.3 mm (3.4 in)
1964	47.5 mm (1.9 in)
1965	51.1 mm (2.0 in)
1966	77.7 mm (3.1 in)
1967	100.1 mm (3.9 in)
1968	98.6 mm (3.9 in)
1969	72.1 mm (2.8 in)
1970	89.9 mm (3.5 in)

Wettest five days (Rx5day)

The wettest five days of the year at Hamilton Af Base, 1934 to 1970. The record is 294.4 mm (11.6 in) in 1955, marked on the chart; the median year is 126.4 mm (5.0 in).

Wettest five days (Rx5day) at Hamilton Af Base by year
Year	Wettest five days (Rx5day)
1934	99.5 mm (3.9 in)
1935	107.0 mm (4.2 in)
1936	0.0 mm (0.00 in)
1937	11.4 mm (0.4 in)
1938	179.0 mm (7.0 in)
1939	49.9 mm (2.0 in)
1940	197.6 mm (7.8 in)
1941	121.4 mm (4.8 in)
1942	133.1 mm (5.2 in)
1943	236.5 mm (9.3 in)
1944	92.4 mm (3.6 in)
1945	140.4 mm (5.5 in)
1946	110.0 mm (4.3 in)
1947	93.8 mm (3.7 in)
1948	72.2 mm (2.8 in)
1949	117.9 mm (4.6 in)
1950	147.2 mm (5.8 in)
1951	129.9 mm (5.1 in)
1952	146.1 mm (5.8 in)
1953	92.7 mm (3.6 in)
1954	137.9 mm (5.4 in)
1955	294.4 mm (11.6 in)
1956	110.0 mm (4.3 in)
1957	108.6 mm (4.3 in)
1958	111.5 mm (4.4 in)
1959	161.5 mm (6.4 in)
1960	78.0 mm (3.1 in)
1961	108.5 mm (4.3 in)
1962	205.0 mm (8.1 in)
1963	214.5 mm (8.4 in)
1964	124.2 mm (4.9 in)
1965	154.2 mm (6.1 in)
1966	156.2 mm (6.1 in)
1967	243.1 mm (9.6 in)
1968	126.4 mm (5.0 in)
1969	168.6 mm (6.6 in)
1970	194.8 mm (7.7 in)

Longest dry spell (CDD)

The longest dry spell of the year at Hamilton Af Base, 1934 to 1970. The record is 174 days in 1943, marked on the chart; the median year is 129 days.

Longest dry spell (CDD) at Hamilton Af Base by year
Year	Longest dry spell (CDD)
1934	109 days
1935	117 days
1936	31 days
1937	17 days
1938	26 days
1939	113 days
1940	129 days
1941	115 days
1942	137 days
1943	174 days
1944	155 days
1945	162 days
1946	142 days
1947	121 days
1948	111 days
1949	100 days
1950	166 days
1951	150 days
1952	137 days
1953	120 days
1954	76 days
1955	136 days
1956	136 days
1957	128 days
1958	132 days
1959	144 days
1960	133 days
1961	145 days
1962	165 days
1963	124 days
1964	140 days
1965	112 days
1966	84 days
1967	106 days
1968	99 days
1969	169 days
1970	130 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

26 years with a frost

Across 26 years with a frost, the median last spring frost at Hamilton Af Base falls on 14 February and the median first autumn frost on 4 December, which leaves a median of 296 days between them.

Fitted over all years, the growing season changes by +0.8 days per decade at this station.

Frost dates and growing season at Hamilton Af Base
Measure	Median, all years	Earliest period	Recent period (1940 to 1970)	Recent against earliest	Fitted trend
Last spring frost	14 February	n/a	14 February	n/a	+0.2 days per decade
First autumn frost	4 December	n/a	4 December	n/a	+1.0 days per decade
Growing days	296 days	n/a	296 days	n/a	+0.8 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

33 years, 1935 to 1970

A day with at least 65.8 mm (2.6 in) of rain is expected about once in 2 years. A day with at least 116.8 mm (4.6 in) of rain is expected about once in 100 years.

Rainfall return levels at Hamilton Af Base: the daily rain expected about once in a given number of years
Expected about once in	A day with at least	Note
2 years	65.8 mm (2.6 in)
5 years	84.5 mm (3.3 in)
10 years	94.5 mm (3.7 in)
25 years	104.9 mm (4.1 in)
50 years	111.3 mm (4.4 in)	Longer than the 33 years of record
100 years	116.8 mm (4.6 in)	Longer than the 33 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, 33 years of values from 1935 to 1970.

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: 100.1 mm (3.9 in) in 1967; 98.8 mm (3.9 in) in 1962; 98.6 mm (3.9 in) in 1968.

Download the Data

Data for Hamilton Af Base standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Hamilton Af Base 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).