Altadena Weather Records (USC00040144)

Record envelope, standing records and threshold days for Altadena (USC00040144), California, United States, with 105 years of record.

Key Facts for Altadena

Altadena (USC00040144) is a weather station in California, United States at 34.18 latitude and -118.14 longitude, 344 m (1,127 ft) above sea level.
The station reports from 1922 to 2026, 105 years of record.
1,464 records set at Altadena still stand.
Records are tracked for prcp, snow, snwd: an element needs 30 years of data to be eligible.
Altadena set a daily record precipitation of 45.0 mm (1.8 in) on 17 February 2026.

About the Station

Location: California, United States, 34.18 latitude, -118.14 longitude.
Elevation: 344 m (1,127 ft).
Period of record: 1922 to 2026, 105 years.
Eligible elements: 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 Altadena. 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 Altadena, with 2026 drawn through them
Month	Highest record high	Lowest record low	2026 highest maximum	2026 lowest minimum
Jan	30.0 C (86.0 F)	-2.8 C (27.0 F)	n/a	n/a
Feb	29.4 C (84.9 F)	-3.3 C (26.1 F)	n/a	n/a
Mar	31.7 C (89.1 F)	-0.6 C (30.9 F)	n/a	n/a
Apr	33.3 C (91.9 F)	0.0 C (32.0 F)	n/a	n/a
May	38.3 C (100.9 F)	2.8 C (37.0 F)	n/a	n/a
Jun	38.3 C (100.9 F)	5.0 C (41.0 F)	n/a	n/a
Jul	41.1 C (106.0 F)	8.9 C (48.0 F)	n/a	n/a
Aug	40.6 C (105.1 F)	10.0 C (50.0 F)	n/a	n/a
Sep	41.1 C (106.0 F)	7.2 C (45.0 F)	n/a	n/a
Oct	37.8 C (100.0 F)	2.8 C (37.0 F)	n/a	n/a
Nov	33.3 C (91.9 F)	2.2 C (36.0 F)	n/a	n/a
Dec	30.0 C (86.0 F)	-1.1 C (30.0 F)	n/a	n/a

Which Years Hold Standing Records

1,464 standing records

1,464 records at Altadena still stand. 1922 holds the most, with 264.

Wettest Day of Each Month

Jan: 229.1 mm (9.0 in)

The wettest day on record for each calendar month at Altadena. The most was 229.1 mm (9.0 in) on 22 January 1943.

Record daily precipitation for each month at Altadena
Month	Record daily precipitation (mm)	Date
Jan	229.1 mm (9.0 in)	22 January 1943
Feb	152.4 mm (6.0 in)	9 February 1998
Mar	211.6 mm (8.3 in)	2 March 1938
Apr	128.8 mm (5.1 in)	5 April 1926
May	57.9 mm (2.3 in)	13 May 1998
Jun	33.0 mm (1.3 in)	17 June 1995
Jul	12.4 mm (0.5 in)	19 July 2015
Aug	125.7 mm (4.9 in)	21 August 2023
Sep	112.8 mm (4.4 in)	25 September 1939
Oct	103.6 mm (4.1 in)	20 October 2004
Nov	172.2 mm (6.8 in)	29 November 1970
Dec	138.4 mm (5.4 in)	29 December 1965

Period of Record Coverage

1922 to 1929

8 years of record at Altadena, 1922 to 1929. 2 years have data for under 90 percent of days and are left out of rankings: 1925, 1926.

Latest Records

Latest records at Altadena
Date	Station	Record	Value	Beat old record by	Old record stood	Significance
17 February 2026	Altadena, US	daily rain	45.0 mm (1.8 in)	0.5 mm (0.02 in)	36 years	20 of 100 (Routine)
25 December 2025	Altadena, US	daily rain	73.7 mm (2.9 in)	21.4 mm (0.8 in)	42 years	32 of 100 (Routine)
15 November 2025	Altadena, US	daily rain	62.0 mm (2.4 in)	18.8 mm (0.7 in)	72 years	40 of 100 (Notable)
15 October 2025	Altadena, US	daily rain	19.1 mm (0.8 in)	11.2 mm (0.4 in)	90 years	20 of 100 (Routine)
14 October 2025	Altadena, US	daily rain	20.3 mm (0.8 in)	2.5 mm (0.10 in)	7 years	13 of 100 (Routine)
28 September 2025	Altadena, US	daily rain	1.3 mm (0.05 in)	0.5 mm (0.02 in)	58 years	20 of 100 (Routine)
14 July 2024	Altadena, US	daily rain	0.3 mm (0.01 in)	0.3 mm (0.01 in)	101 years	20 of 100 (Routine)
6 February 2024	Altadena, US	daily rain	83.8 mm (3.3 in)	2.5 mm (0.10 in)	86 years	36 of 100 (Notable)
5 February 2024	Altadena, US	daily rain	106.2 mm (4.2 in)	83.6 mm (3.3 in)	4 years	44 of 100 (Notable)
21 August 2023	Altadena, US	monthly rain	125.7 mm (4.9 in)	68.0 mm (2.7 in)	46 years	73 of 100 (Major)
20 August 2023	Altadena, US	daily rain	2.5 mm (0.10 in)	2.5 mm (0.10 in)	100 years	20 of 100 (Routine)
11 June 2023	Altadena, US	daily rain	5.8 mm (0.23 in)	0.5 mm (0.02 in)	60 years	20 of 100 (Routine)
4 May 2023	Altadena, US	daily rain	33.5 mm (1.3 in)	17.8 mm (0.7 in)	24 years	40 of 100 (Notable)
15 March 2023	Altadena, US	daily rain	83.8 mm (3.3 in)	14.7 mm (0.6 in)	70 years	38 of 100 (Notable)
11 December 2022	Altadena, US	daily rain	63.5 mm (2.5 in)	12.7 mm (0.5 in)	25 years	23 of 100 (Routine)
8 November 2022	Altadena, US	daily rain	33.0 mm (1.3 in)	2.5 mm (0.10 in)	37 years	22 of 100 (Routine)
9 September 2022	Altadena, US	daily rain	4.3 mm (0.17 in)	2.0 mm (0.08 in)	40 years	20 of 100 (Routine)
22 June 2022	Altadena, US	daily rain (Tie)	2.5 mm (0.10 in)	tie	76 years	8 of 100 (Routine)
29 March 2022	Altadena, US	daily rain	55.9 mm (2.2 in)	4.6 mm (0.18 in)	16 years	16 of 100 (Routine)
26 October 2021	Altadena, US	daily rain	29.7 mm (1.2 in)	2.8 mm (0.11 in)	80 years	36 of 100 (Notable)

Extremes by Year

1922 to 2026

Yearly extremes at Altadena: the record and the median year
Measure	Record	Year of the record	Median year	Years with a value
Hottest day (TXx)	41.1 C (106.0 F)	1927	37.2 C (99.0 F)	8
Coldest night (TNn)	-3.3 C (26.1 F)	1929	-1.1 C (30.0 F)	9
Wettest day (Rx1day)	229.1 mm (9.0 in)	1943	73.7 mm (2.9 in)	99
Wettest five days (Rx5day)	426.5 mm (16.8 in)	1969	118.2 mm (4.7 in)	99
Longest dry spell (CDD)	219 days	1970	103 days	99

Hottest day (TXx)

The hottest day of the year at Altadena, 1922 to 2026. The record is 41.1 C (106.0 F) in 1927, marked on the chart; the median year is 37.2 C (99.0 F).

Hottest day (TXx) at Altadena by year
Year	Hottest day (TXx)
1922	36.1 C (97.0 F)
1923	37.2 C (99.0 F)
1924	37.2 C (99.0 F)
1925	32.2 C (90.0 F)
1926	32.2 C (90.0 F)
1927	41.1 C (106.0 F)
1928	40.0 C (104.0 F)
1929	41.1 C (106.0 F)
1932	n/a
1933	n/a
1934	n/a
1935	n/a
1936	n/a
1937	n/a
1938	n/a
1939	n/a
1940	n/a
1941	n/a
1942	n/a
1943	n/a
1944	n/a
1945	n/a
1946	n/a
1947	n/a
1949	n/a
1950	n/a
1951	n/a
1952	n/a
1953	n/a
1954	n/a
1955	n/a
1956	n/a
1957	n/a
1958	n/a
1959	n/a
1960	n/a
1961	n/a
1962	n/a
1963	n/a
1964	n/a
1965	n/a
1966	n/a
1967	n/a
1968	n/a
1969	n/a
1970	n/a
1971	n/a
1972	n/a
1973	n/a
1974	n/a
1975	n/a
1976	n/a
1977	n/a
1978	n/a
1979	n/a
1980	n/a
1981	n/a
1982	n/a
1983	n/a
1984	n/a
1985	n/a
1986	n/a
1987	n/a
1988	n/a
1989	n/a
1990	n/a
1991	n/a
1992	n/a
1993	n/a
1994	n/a
1995	n/a
1996	n/a
1997	n/a
1998	n/a
1999	n/a
2000	n/a
2004	n/a
2005	n/a
2006	n/a
2007	n/a
2008	n/a
2009	n/a
2010	n/a
2011	n/a
2012	n/a
2013	n/a
2014	n/a
2015	n/a
2016	n/a
2017	n/a
2018	n/a
2019	n/a
2020	n/a
2021	n/a
2022	n/a
2023	n/a
2024	n/a
2025	n/a
2026	n/a

Coldest night (TNn)

The coldest night of the year at Altadena, 1922 to 2026. The record is -3.3 C (26.1 F) in 1929, marked on the chart; the median year is -1.1 C (30.0 F).

Coldest night (TNn) at Altadena by year
Year	Coldest night (TNn)
1922	-1.7 C (28.9 F)
1923	-1.1 C (30.0 F)
1924	-2.8 C (27.0 F)
1925	1.1 C (34.0 F)
1926	3.3 C (37.9 F)
1927	0.0 C (32.0 F)
1928	-1.1 C (30.0 F)
1929	-3.3 C (26.1 F)
1932	-2.8 C (27.0 F)
1933	n/a
1934	n/a
1935	n/a
1936	n/a
1937	n/a
1938	n/a
1939	n/a
1940	n/a
1941	n/a
1942	n/a
1943	n/a
1944	n/a
1945	n/a
1946	n/a
1947	n/a
1949	n/a
1950	n/a
1951	n/a
1952	n/a
1953	n/a
1954	n/a
1955	n/a
1956	n/a
1957	n/a
1958	n/a
1959	n/a
1960	n/a
1961	n/a
1962	n/a
1963	n/a
1964	n/a
1965	n/a
1966	n/a
1967	n/a
1968	n/a
1969	n/a
1970	n/a
1971	n/a
1972	n/a
1973	n/a
1974	n/a
1975	n/a
1976	n/a
1977	n/a
1978	n/a
1979	n/a
1980	n/a
1981	n/a
1982	n/a
1983	n/a
1984	n/a
1985	n/a
1986	n/a
1987	n/a
1988	n/a
1989	n/a
1990	n/a
1991	n/a
1992	n/a
1993	n/a
1994	n/a
1995	n/a
1996	n/a
1997	n/a
1998	n/a
1999	n/a
2000	n/a
2004	n/a
2005	n/a
2006	n/a
2007	n/a
2008	n/a
2009	n/a
2010	n/a
2011	n/a
2012	n/a
2013	n/a
2014	n/a
2015	n/a
2016	n/a
2017	n/a
2018	n/a
2019	n/a
2020	n/a
2021	n/a
2022	n/a
2023	n/a
2024	n/a
2025	n/a
2026	n/a

Wettest day (Rx1day)

The wettest day of the year at Altadena, 1922 to 2026. The record is 229.1 mm (9.0 in) in 1943, marked on the chart; the median year is 73.7 mm (2.9 in).

Wettest day (Rx1day) at Altadena by year
Year	Wettest day (Rx1day)
1922	90.2 mm (3.6 in)
1923	30.0 mm (1.2 in)
1924	41.1 mm (1.6 in)
1925	56.9 mm (2.2 in)
1926	128.8 mm (5.1 in)
1927	113.0 mm (4.4 in)
1928	66.8 mm (2.6 in)
1929	82.3 mm (3.2 in)
1932	62.0 mm (2.4 in)
1933	115.6 mm (4.6 in)
1934	162.8 mm (6.4 in)
1935	68.8 mm (2.7 in)
1936	73.2 mm (2.9 in)
1937	81.3 mm (3.2 in)
1938	211.6 mm (8.3 in)
1939	112.8 mm (4.4 in)
1940	73.2 mm (2.9 in)
1941	146.1 mm (5.8 in)
1942	26.9 mm (1.1 in)
1943	229.1 mm (9.0 in)
1944	135.1 mm (5.3 in)
1945	113.0 mm (4.4 in)
1946	81.8 mm (3.2 in)
1947	37.3 mm (1.5 in)
1949	58.4 mm (2.3 in)
1950	45.2 mm (1.8 in)
1951	61.0 mm (2.4 in)
1952	123.2 mm (4.9 in)
1953	25.7 mm (1.0 in)
1954	64.8 mm (2.6 in)
1955	41.1 mm (1.6 in)
1956	170.7 mm (6.7 in)
1957	67.3 mm (2.6 in)
1958	84.8 mm (3.3 in)
1959	95.5 mm (3.8 in)
1960	41.1 mm (1.6 in)
1961	53.8 mm (2.1 in)
1962	92.5 mm (3.6 in)
1963	72.4 mm (2.9 in)
1964	47.0 mm (1.9 in)
1965	138.4 mm (5.4 in)
1966	89.4 mm (3.5 in)
1967	88.4 mm (3.5 in)
1968	74.9 mm (2.9 in)
1969	201.9 mm (7.9 in)
1970	172.2 mm (6.8 in)
1971	71.4 mm (2.8 in)
1972	36.6 mm (1.4 in)
1973	126.0 mm (5.0 in)
1974	81.3 mm (3.2 in)
1975	65.5 mm (2.6 in)
1976	71.4 mm (2.8 in)
1977	94.0 mm (3.7 in)
1978	112.3 mm (4.4 in)
1979	68.6 mm (2.7 in)
1980	109.2 mm (4.3 in)
1981	44.2 mm (1.7 in)
1982	73.7 mm (2.9 in)
1983	145.8 mm (5.7 in)
1984	65.3 mm (2.6 in)
1985	50.8 mm (2.0 in)
1986	70.9 mm (2.8 in)
1987	57.9 mm (2.3 in)
1988	86.4 mm (3.4 in)
1989	44.7 mm (1.8 in)
1990	44.5 mm (1.8 in)
1991	121.4 mm (4.8 in)
1992	139.7 mm (5.5 in)
1993	86.4 mm (3.4 in)
1994	38.4 mm (1.5 in)
1995	126.2 mm (5.0 in)
1996	95.5 mm (3.8 in)
1997	67.1 mm (2.6 in)
1998	152.4 mm (6.0 in)
1999	50.0 mm (2.0 in)
2000	81.3 mm (3.2 in)
2004	107.4 mm (4.2 in)
2005	120.7 mm (4.8 in)
2006	67.1 mm (2.6 in)
2007	39.4 mm (1.6 in)
2008	126.5 mm (5.0 in)
2009	75.9 mm (3.0 in)
2010	88.4 mm (3.5 in)
2011	99.1 mm (3.9 in)
2012	33.8 mm (1.3 in)
2013	30.5 mm (1.2 in)
2014	43.7 mm (1.7 in)
2015	41.7 mm (1.6 in)
2016	50.3 mm (2.0 in)
2017	84.1 mm (3.3 in)
2018	44.2 mm (1.7 in)
2019	80.3 mm (3.2 in)
2020	48.3 mm (1.9 in)
2021	59.4 mm (2.3 in)
2022	63.5 mm (2.5 in)
2023	125.7 mm (4.9 in)
2024	106.2 mm (4.2 in)
2025	73.7 mm (2.9 in)
2026	62.7 mm (2.5 in)

Wettest five days (Rx5day)

The wettest five days of the year at Altadena, 1922 to 2026. The record is 426.5 mm (16.8 in) in 1969, marked on the chart; the median year is 118.2 mm (4.7 in).

Wettest five days (Rx5day) at Altadena by year
Year	Wettest five days (Rx5day)
1922	95.5 mm (3.8 in)
1923	43.4 mm (1.7 in)
1924	66.6 mm (2.6 in)
1925	50.8 mm (2.0 in)
1926	313.9 mm (12.4 in)
1927	271.3 mm (10.7 in)
1928	75.2 mm (3.0 in)
1929	91.5 mm (3.6 in)
1932	98.9 mm (3.9 in)
1933	249.5 mm (9.8 in)
1934	289.3 mm (11.4 in)
1935	76.5 mm (3.0 in)
1936	166.1 mm (6.5 in)
1937	96.1 mm (3.8 in)
1938	399.8 mm (15.7 in)
1939	160.1 mm (6.3 in)
1940	100.3 mm (3.9 in)
1941	233.9 mm (9.2 in)
1942	50.8 mm (2.0 in)
1943	396.8 mm (15.6 in)
1944	251.4 mm (9.9 in)
1945	189.0 mm (7.4 in)
1946	154.4 mm (6.1 in)
1947	47.4 mm (1.9 in)
1949	75.4 mm (3.0 in)
1950	59.4 mm (2.3 in)
1951	109.9 mm (4.3 in)
1952	254.3 mm (10.0 in)
1953	37.0 mm (1.5 in)
1954	86.7 mm (3.4 in)
1955	66.1 mm (2.6 in)
1956	226.8 mm (8.9 in)
1957	81.8 mm (3.2 in)
1958	170.2 mm (6.7 in)
1959	95.5 mm (3.8 in)
1960	74.2 mm (2.9 in)
1961	70.4 mm (2.8 in)
1962	237.0 mm (9.3 in)
1963	124.7 mm (4.9 in)
1964	73.9 mm (2.9 in)
1965	227.1 mm (8.9 in)
1966	197.1 mm (7.8 in)
1967	190.8 mm (7.5 in)
1968	82.5 mm (3.2 in)
1969	426.5 mm (16.8 in)
1970	203.2 mm (8.0 in)
1971	144.4 mm (5.7 in)
1972	63.5 mm (2.5 in)
1973	194.6 mm (7.7 in)
1974	246.7 mm (9.7 in)
1975	115.0 mm (4.5 in)
1976	121.4 mm (4.8 in)
1977	142.1 mm (5.6 in)
1978	297.7 mm (11.7 in)
1979	115.2 mm (4.5 in)
1980	135.9 mm (5.4 in)
1981	99.3 mm (3.9 in)
1982	88.3 mm (3.5 in)
1983	343.1 mm (13.5 in)
1984	128.0 mm (5.0 in)
1985	82.8 mm (3.3 in)
1986	92.5 mm (3.6 in)
1987	92.9 mm (3.7 in)
1988	79.6 mm (3.1 in)
1989	53.8 mm (2.1 in)
1990	85.6 mm (3.4 in)
1991	245.9 mm (9.7 in)
1992	274.6 mm (10.8 in)
1993	167.2 mm (6.6 in)
1994	70.4 mm (2.8 in)
1995	228.1 mm (9.0 in)
1996	197.9 mm (7.8 in)
1997	78.5 mm (3.1 in)
1998	186.9 mm (7.4 in)
1999	65.0 mm (2.6 in)
2000	125.0 mm (4.9 in)
2004	200.3 mm (7.9 in)
2005	371.1 mm (14.6 in)
2006	113.2 mm (4.5 in)
2007	39.4 mm (1.6 in)
2008	185.5 mm (7.3 in)
2009	132.4 mm (5.2 in)
2010	256.8 mm (10.1 in)
2011	135.0 mm (5.3 in)
2012	30.3 mm (1.2 in)
2013	44.2 mm (1.7 in)
2014	115.9 mm (4.6 in)
2015	60.5 mm (2.4 in)
2016	90.0 mm (3.5 in)
2017	136.3 mm (5.4 in)
2018	70.1 mm (2.8 in)
2019	151.3 mm (6.0 in)
2020	118.2 mm (4.7 in)
2021	97.8 mm (3.9 in)
2022	93.7 mm (3.7 in)
2023	128.2 mm (5.0 in)
2024	249.7 mm (9.8 in)
2025	179.4 mm (7.1 in)
2026	113.3 mm (4.5 in)

Longest dry spell (CDD)

The longest dry spell of the year at Altadena, 1922 to 2026. The record is 219 days in 1970, marked on the chart; the median year is 103 days.

Longest dry spell (CDD) at Altadena by year
Year	Longest dry spell (CDD)
1922	35 days
1923	84 days
1924	87 days
1925	96 days
1926	26 days
1927	85 days
1928	40 days
1929	104 days
1932	116 days
1933	94 days
1934	89 days
1935	61 days
1936	67 days
1937	187 days
1938	90 days
1939	132 days
1940	74 days
1941	77 days
1942	103 days
1943	127 days
1944	95 days
1945	70 days
1946	132 days
1947	76 days
1949	149 days
1950	69 days
1951	106 days
1952	84 days
1953	140 days
1954	137 days
1955	101 days
1956	146 days
1957	122 days
1958	127 days
1959	162 days
1960	158 days
1961	103 days
1962	99 days
1963	84 days
1964	140 days
1965	55 days
1966	70 days
1967	77 days
1968	73 days
1969	141 days
1970	219 days
1971	136 days
1972	72 days
1973	115 days
1974	121 days
1975	108 days
1976	99 days
1977	68 days
1978	132 days
1979	85 days
1980	64 days
1981	126 days
1982	82 days
1983	74 days
1984	96 days
1985	140 days
1986	165 days
1987	43 days
1988	54 days
1989	124 days
1990	175 days
1991	111 days
1992	102 days
1993	127 days
1994	110 days
1995	137 days
1996	194 days
1997	104 days
1998	143 days
1999	158 days
2000	96 days
2004	182 days
2005	136 days
2006	130 days
2007	91 days
2008	128 days
2009	101 days
2010	135 days
2011	61 days
2012	91 days
2013	152 days
2014	188 days
2015	56 days
2016	126 days
2017	106 days
2018	134 days
2019	93 days
2020	172 days
2021	70 days
2022	78 days
2023	69 days
2024	175 days
2025	88 days
2026	64 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.

Rainfall Return Levels

87 years, 1923 to 2025

A day with at least 75.8 mm (3.0 in) of rain is expected about once in 2 years. A day with at least 240.6 mm (9.5 in) of rain is expected about once in 100 years.

Rainfall return levels at Altadena: the daily rain expected about once in a given number of years
Expected about once in	A day with at least	Note
2 years	75.8 mm (3.0 in)
5 years	114.0 mm (4.5 in)
10 years	141.5 mm (5.6 in)
25 years	179.0 mm (7.0 in)
50 years	209.0 mm (8.2 in)
100 years	240.6 mm (9.5 in)	Longer than the 87 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, 87 years of values from 1923 to 2025.

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: 229.1 mm (9.0 in) in 1943; 211.6 mm (8.3 in) in 1938; 201.9 mm (7.9 in) in 1969.

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Data for Altadena standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Altadena 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.

Data as of 2026-10-12. Last revised 12 October 2026 (2026-10-12).

Year	Days with data	Share of year	Complete
1922	346	95%	Yes
1923	352	96%	Yes
1924	365	100%	Yes
1925	242	66%	No
1926	151	41%	No
1927	332	91%	Yes
1928	366	100%	Yes
1929	365	100%	Yes