Copco #1 Dam Weather Records (USC00041990)

Record envelope, standing records and threshold days for Copco #1 Dam (USC00041990), California, United States, with 65 years of record.

Key Facts for Copco #1 Dam

Copco #1 Dam (USC00041990) is a weather station in California, United States at 41.98 latitude and -122.34 longitude, 812 m (2,665 ft) above sea level.
The station reports from 1959 to 2023, 65 years of record.
1,464 records set at Copco #1 Dam still stand.
Records are tracked for prcp, snow, snwd: an element needs 30 years of data to be eligible.
Copco #1 Dam set a daily record snow depth of 2.5 cm (1.0 in) on 8 March 2023.

About the Station

Location: California, United States, 41.98 latitude, -122.34 longitude.
Elevation: 812 m (2,665 ft).
Period of record: 1959 to 2023, 65 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 Copco #1 Dam. 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 Copco #1 Dam, with 2026 drawn through them
Month	Highest record high	Lowest record low	2026 highest maximum	2026 lowest minimum
Jan	18.3 C (64.9 F)	-18.3 C (-0.9 F)	n/a	n/a
Feb	23.3 C (73.9 F)	-11.7 C (10.9 F)	n/a	n/a
Mar	26.7 C (80.1 F)	-11.1 C (12.0 F)	n/a	n/a
Apr	31.1 C (88.0 F)	-8.9 C (16.0 F)	n/a	n/a
May	35.6 C (96.1 F)	-6.7 C (19.9 F)	n/a	n/a
Jun	43.3 C (109.9 F)	-3.9 C (25.0 F)	n/a	n/a
Jul	45.0 C (113.0 F)	6.1 C (43.0 F)	n/a	n/a
Aug	43.3 C (109.9 F)	5.0 C (41.0 F)	n/a	n/a
Sep	40.6 C (105.1 F)	0.6 C (33.1 F)	n/a	n/a
Oct	36.1 C (97.0 F)	-6.7 C (19.9 F)	n/a	n/a
Nov	25.0 C (77.0 F)	-9.4 C (15.1 F)	n/a	n/a
Dec	17.2 C (63.0 F)	-18.9 C (-2.0 F)	n/a	n/a

Which Years Hold Standing Records

1,464 standing records

1,464 records at Copco #1 Dam still stand. 2011 holds the most, with 193.

All-Time Record Progression

3 new records

3 all-time records were set at Copco #1 Dam between 22 February 2007 and 27 January 2008. Each dot is a new record.

When Copco #1 Dam set new all-time records
Date	Kind	Detail
2007-02-22	Record daily snowfall	Record daily snowfall 40.6 cm (16.0 in)
2007-02-22	Record snow depth	Record snow depth 40.6 cm (16.0 in)
2008-01-27	Record daily precipitation	Record daily precipitation 76.2 mm (3.0 in)

Wettest Day of Each Month

Jan: 76.2 mm (3.0 in)

The wettest day on record for each calendar month at Copco #1 Dam. The most was 76.2 mm (3.0 in) on 27 January 2008.

Record daily precipitation for each month at Copco #1 Dam
Month	Record daily precipitation (mm)	Date
Jan	76.2 mm (3.0 in)	27 January 2008
Feb	55.4 mm (2.2 in)	21 February 1982
Mar	54.6 mm (2.1 in)	18 March 1975
Apr	49.3 mm (1.9 in)	30 April 2002
May	38.4 mm (1.5 in)	31 May 1993
Jun	45.7 mm (1.8 in)	11 June 1997
Jul	31.8 mm (1.3 in)	1 July 2012
Aug	50.8 mm (2.0 in)	23 August 1983
Sep	40.6 mm (1.6 in)	17 September 1989
Oct	66.0 mm (2.6 in)	16 October 2016
Nov	54.9 mm (2.2 in)	25 November 1961
Dec	73.7 mm (2.9 in)	22 December 1964

Period of Record Coverage

1969 to 2023

18 years of record at Copco #1 Dam, 1969 to 2023. 7 years have data for under 90 percent of days and are left out of rankings: 1969, 1970, 1977, 1979, 1981, 2022, 2023.

Days with data per year at Copco #1 Dam
Year	Days with data	Share of year	Complete
1969	31	8%	No
1970	30	8%	No
1977	1	0%	No
1979	1	0%	No
1981	29	8%	No
2011	363	99%	Yes
2012	359	98%	Yes
2013	363	99%	Yes
2014	360	99%	Yes
2015	344	94%	Yes
2016	346	95%	Yes
2017	337	92%	Yes
2018	342	94%	Yes
2019	360	99%	Yes
2020	343	94%	Yes
2021	346	95%	Yes
2022	318	87%	No
2023	71	19%	No

Latest Records

Latest records at Copco #1 Dam
Date	Station	Record	Value	Beat old record by	Old record stood	Significance
8 March 2023	Copco #1 Dam, US	daily snow depth	2.5 cm (1.0 in)	2.5 cm (1.0 in)	62 years	20 of 100 (Routine)
7 March 2023	Copco #1 Dam, US	daily rain	22.9 mm (0.9 in)	4.9 mm (0.19 in)	52 years	20 of 100 (Routine)
7 March 2023	Copco #1 Dam, US	daily snow depth (Tie)	2.5 cm (1.0 in)	tie	48 years	5 of 100 (Routine)
5 March 2023	Copco #1 Dam, US	daily snow depth	2.5 cm (1.0 in)	2.5 cm (1.0 in)	62 years	20 of 100 (Routine)
4 March 2023	Copco #1 Dam, US	daily snow depth	5.1 cm (2.0 in)	5.1 cm (2.0 in)	62 years	20 of 100 (Routine)
4 March 2023	Copco #1 Dam, US	daily snowfall	3.8 cm (1.5 in)	1.3 cm (0.5 in)	33 years	20 of 100 (Routine)
14 February 2023	Copco #1 Dam, US	daily snowfall	8.1 cm (3.2 in)	6.8 cm (2.7 in)	56 years	35 of 100 (Notable)
14 February 2023	Copco #1 Dam, US	daily snow depth	7.6 cm (3.0 in)	7.6 cm (3.0 in)	63 years	20 of 100 (Routine)
20 September 2022	Copco #1 Dam, US	daily rain	8.6 mm (0.34 in)	4.5 mm (0.18 in)	52 years	20 of 100 (Routine)
4 July 2022	Copco #1 Dam, US	daily rain	3.6 mm (0.14 in)	1.8 mm (0.07 in)	57 years	20 of 100 (Routine)
3 July 2022	Copco #1 Dam, US	daily rain	1.3 mm (0.05 in)	0.3 mm (0.01 in)	35 years	16 of 100 (Routine)
16 April 2022	Copco #1 Dam, US	daily rain	10.9 mm (0.4 in)	1.0 mm (0.04 in)	17 years	12 of 100 (Routine)
12 April 2022	Copco #1 Dam, US	daily snowfall	1.8 cm (0.7 in)	1.8 cm (0.7 in)	61 years	20 of 100 (Routine)
12 April 2022	Copco #1 Dam, US	daily snow depth	2.5 cm (1.0 in)	2.5 cm (1.0 in)	61 years	20 of 100 (Routine)
11 April 2022	Copco #1 Dam, US	daily snowfall	2.5 cm (1.0 in)	2.5 cm (1.0 in)	61 years	20 of 100 (Routine)
11 April 2022	Copco #1 Dam, US	daily snow depth	2.5 cm (1.0 in)	2.5 cm (1.0 in)	61 years	20 of 100 (Routine)
16 December 2021	Copco #1 Dam, US	daily snowfall (Tie)	2.5 cm (1.0 in)	tie	51 years	5 of 100 (Routine)
11 October 2021	Copco #1 Dam, US	daily rain	15.2 mm (0.6 in)	2.2 mm (0.09 in)	60 years	20 of 100 (Routine)
28 September 2021	Copco #1 Dam, US	daily rain	15.5 mm (0.6 in)	1.3 mm (0.05 in)	59 years	20 of 100 (Routine)
10 September 2021	Copco #1 Dam, US	daily rain	8.9 mm (0.35 in)	3.6 mm (0.14 in)	43 years	20 of 100 (Routine)

Climate Trend

12 complete years, 2011 to 2022

One stripe for each of 12 complete years at Copco #1 Dam, 2011 to 2022. Blue stripes are years cooler than the station's own mean of 12.4 C (54.4 F); red stripes are warmer. The coolest year was 2011, at 10.2 C (50.3 F), and the warmest was 2014, at 13.5 C (56.4 F). The strongest colour marks a difference of 2.3 C (4.1 F).

Annual mean temperature at Copco #1 Dam as warming stripes, 2011 to 2022
Year	Annual mean temperature	Difference from the station mean
2011	10.2 C	-2.26 C
2012	12.0 C	-0.40 C
2013	12.1 C	-0.39 C
2014	13.5 C	+1.10 C
2015	13.5 C	+1.01 C
2016	12.6 C	+0.16 C
2017	11.8 C	-0.62 C
2018	12.8 C	+0.37 C
2019	12.2 C	-0.26 C
2020	12.9 C	+0.44 C
2021	13.0 C	+0.60 C
2022	12.7 C	+0.22 C

This station does not have enough complete years (30 are needed) to fit a temperature trend.

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

1959 to 2023

Yearly extremes at Copco #1 Dam: the record and the median year
Measure	Record	Year of the record	Median year	Years with a value
Hottest day (TXx)	45.0 C (113.0 F)	2022	40.3 C (104.5 F)	18
Coldest night (TNn)	-18.9 C (-2.0 F)	2013	-9.7 C (14.5 F)	18
Wettest day (Rx1day)	76.2 mm (3.0 in)	2008	37.1 mm (1.5 in)	65
Wettest five days (Rx5day)	158.8 mm (6.3 in)	1964	74.2 mm (2.9 in)	65
Longest dry spell (CDD)	158 days	2002	51 days	65

Hottest day (TXx)

The hottest day of the year at Copco #1 Dam, 1959 to 2023. The record is 45.0 C (113.0 F) in 2022, marked on the chart; the median year is 40.3 C (104.5 F).

Hottest day (TXx) at Copco #1 Dam by year
Year	Hottest day (TXx)
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	35.0 C (95.0 F)
1970	36.1 C (97.0 F)
1971	n/a
1972	n/a
1973	n/a
1974	n/a
1975	n/a
1976	n/a
1977	10.6 C (51.1 F)
1978	n/a
1979	3.9 C (39.0 F)
1980	n/a
1981	17.2 C (63.0 F)
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
2001	n/a
2002	n/a
2003	n/a
2004	n/a
2005	n/a
2006	n/a
2007	n/a
2008	n/a
2009	n/a
2010	n/a
2011	37.2 C (99.0 F)
2012	40.6 C (105.1 F)
2013	41.1 C (106.0 F)
2014	41.1 C (106.0 F)
2015	42.2 C (108.0 F)
2016	41.1 C (106.0 F)
2017	43.3 C (109.9 F)
2018	40.0 C (104.0 F)
2019	40.0 C (104.0 F)
2020	40.6 C (105.1 F)
2021	43.3 C (109.9 F)
2022	45.0 C (113.0 F)
2023	16.1 C (61.0 F)

Coldest night (TNn)

The coldest night of the year at Copco #1 Dam, 1959 to 2023. The record is -18.9 C (-2.0 F) in 2013, marked on the chart; the median year is -9.7 C (14.5 F).

Coldest night (TNn) at Copco #1 Dam by year
Year	Coldest night (TNn)
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	0.6 C (33.1 F)
1970	-1.7 C (28.9 F)
1971	n/a
1972	n/a
1973	n/a
1974	n/a
1975	n/a
1976	n/a
1977	1.1 C (34.0 F)
1978	n/a
1979	-1.1 C (30.0 F)
1980	n/a
1981	-6.7 C (19.9 F)
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
2001	n/a
2002	n/a
2003	n/a
2004	n/a
2005	n/a
2006	n/a
2007	n/a
2008	n/a
2009	n/a
2010	n/a
2011	-16.1 C (3.0 F)
2012	-11.1 C (12.0 F)
2013	-18.9 C (-2.0 F)
2014	-8.3 C (17.1 F)
2015	-8.3 C (17.1 F)
2016	-11.1 C (12.0 F)
2017	-18.3 C (-0.9 F)
2018	-11.7 C (10.9 F)
2019	-9.4 C (15.1 F)
2020	-8.3 C (17.1 F)
2021	-10.6 C (12.9 F)
2022	-10.0 C (14.0 F)
2023	-10.0 C (14.0 F)

Wettest day (Rx1day)

The wettest day of the year at Copco #1 Dam, 1959 to 2023. The record is 76.2 mm (3.0 in) in 2008, marked on the chart; the median year is 37.1 mm (1.5 in).

Wettest day (Rx1day) at Copco #1 Dam by year
Year	Wettest day (Rx1day)
1959	29.2 mm (1.1 in)
1960	50.3 mm (2.0 in)
1961	54.9 mm (2.2 in)
1962	38.4 mm (1.5 in)
1963	28.4 mm (1.1 in)
1964	74.9 mm (2.9 in)
1965	21.3 mm (0.8 in)
1966	49.3 mm (1.9 in)
1967	27.9 mm (1.1 in)
1968	19.1 mm (0.8 in)
1969	49.3 mm (1.9 in)
1970	36.8 mm (1.4 in)
1971	27.7 mm (1.1 in)
1972	59.4 mm (2.3 in)
1973	41.1 mm (1.6 in)
1974	57.7 mm (2.3 in)
1975	54.6 mm (2.1 in)
1976	37.3 mm (1.5 in)
1977	35.8 mm (1.4 in)
1978	28.7 mm (1.1 in)
1979	30.5 mm (1.2 in)
1980	29.0 mm (1.1 in)
1981	37.6 mm (1.5 in)
1982	55.4 mm (2.2 in)
1983	50.8 mm (2.0 in)
1984	26.9 mm (1.1 in)
1985	33.5 mm (1.3 in)
1986	26.9 mm (1.1 in)
1987	27.9 mm (1.1 in)
1988	29.2 mm (1.1 in)
1989	40.6 mm (1.6 in)
1990	52.8 mm (2.1 in)
1991	23.6 mm (0.9 in)
1992	22.4 mm (0.9 in)
1993	38.4 mm (1.5 in)
1994	37.1 mm (1.5 in)
1995	41.4 mm (1.6 in)
1996	35.6 mm (1.4 in)
1997	45.7 mm (1.8 in)
1998	39.9 mm (1.6 in)
1999	40.6 mm (1.6 in)
2000	50.8 mm (2.0 in)
2001	36.8 mm (1.4 in)
2002	64.0 mm (2.5 in)
2003	19.1 mm (0.8 in)
2004	42.9 mm (1.7 in)
2005	39.4 mm (1.6 in)
2006	31.2 mm (1.2 in)
2007	49.0 mm (1.9 in)
2008	76.2 mm (3.0 in)
2009	24.9 mm (1.0 in)
2010	50.8 mm (2.0 in)
2011	26.4 mm (1.0 in)
2012	45.5 mm (1.8 in)
2013	21.1 mm (0.8 in)
2014	33.0 mm (1.3 in)
2015	32.5 mm (1.3 in)
2016	66.0 mm (2.6 in)
2017	17.8 mm (0.7 in)
2018	17.0 mm (0.7 in)
2019	38.1 mm (1.5 in)
2020	32.8 mm (1.3 in)
2021	37.3 mm (1.5 in)
2022	20.3 mm (0.8 in)
2023	25.4 mm (1.0 in)

Wettest five days (Rx5day)

The wettest five days of the year at Copco #1 Dam, 1959 to 2023. The record is 158.8 mm (6.3 in) in 1964, marked on the chart; the median year is 74.2 mm (2.9 in).

Wettest five days (Rx5day) at Copco #1 Dam by year
Year	Wettest five days (Rx5day)
1959	31.7 mm (1.2 in)
1960	96.3 mm (3.8 in)
1961	82.0 mm (3.2 in)
1962	46.1 mm (1.8 in)
1963	76.0 mm (3.0 in)
1964	158.8 mm (6.3 in)
1965	41.2 mm (1.6 in)
1966	87.2 mm (3.4 in)
1967	47.7 mm (1.9 in)
1968	48.7 mm (1.9 in)
1969	105.1 mm (4.1 in)
1970	99.8 mm (3.9 in)
1971	60.6 mm (2.4 in)
1972	111.0 mm (4.4 in)
1973	68.2 mm (2.7 in)
1974	84.9 mm (3.3 in)
1975	76.8 mm (3.0 in)
1976	53.6 mm (2.1 in)
1977	76.5 mm (3.0 in)
1978	49.8 mm (2.0 in)
1979	50.9 mm (2.0 in)
1980	74.2 mm (2.9 in)
1981	105.9 mm (4.2 in)
1982	74.9 mm (2.9 in)
1983	61.9 mm (2.4 in)
1984	45.3 mm (1.8 in)
1985	52.1 mm (2.1 in)
1986	94.1 mm (3.7 in)
1987	52.5 mm (2.1 in)
1988	67.2 mm (2.6 in)
1989	50.0 mm (2.0 in)
1990	89.6 mm (3.5 in)
1991	46.6 mm (1.8 in)
1992	64.6 mm (2.5 in)
1993	73.0 mm (2.9 in)
1994	42.2 mm (1.7 in)
1995	113.5 mm (4.5 in)
1996	81.7 mm (3.2 in)
1997	137.7 mm (5.4 in)
1998	106.0 mm (4.2 in)
1999	60.6 mm (2.4 in)
2000	91.1 mm (3.6 in)
2001	50.8 mm (2.0 in)
2002	103.4 mm (4.1 in)
2003	98.8 mm (3.9 in)
2004	86.0 mm (3.4 in)
2005	116.1 mm (4.6 in)
2006	83.2 mm (3.3 in)
2007	96.7 mm (3.8 in)
2008	123.9 mm (4.9 in)
2009	44.7 mm (1.8 in)
2010	78.7 mm (3.1 in)
2011	77.7 mm (3.1 in)
2012	88.7 mm (3.5 in)
2013	40.7 mm (1.6 in)
2014	72.8 mm (2.9 in)
2015	71.3 mm (2.8 in)
2016	121.9 mm (4.8 in)
2017	44.6 mm (1.8 in)
2018	39.1 mm (1.5 in)
2019	82.5 mm (3.2 in)
2020	54.1 mm (2.1 in)
2021	61.9 mm (2.4 in)
2022	41.7 mm (1.6 in)
2023	61.8 mm (2.4 in)

Longest dry spell (CDD)

The longest dry spell of the year at Copco #1 Dam, 1959 to 2023. The record is 158 days in 2002, marked on the chart; the median year is 51 days.

Longest dry spell (CDD) at Copco #1 Dam by year
Year	Longest dry spell (CDD)
1959	54 days
1960	68 days
1961	41 days
1962	64 days
1963	62 days
1964	56 days
1965	40 days
1966	42 days
1967	87 days
1968	56 days
1969	55 days
1970	111 days
1971	51 days
1972	67 days
1973	88 days
1974	82 days
1975	38 days
1976	30 days
1977	38 days
1978	66 days
1979	42 days
1980	50 days
1981	104 days
1982	51 days
1983	32 days
1984	83 days
1985	56 days
1986	77 days
1987	60 days
1988	43 days
1989	53 days
1990	30 days
1991	37 days
1992	57 days
1993	46 days
1994	49 days
1995	68 days
1996	28 days
1997	20 days
1998	43 days
1999	64 days
2000	35 days
2001	44 days
2002	158 days
2003	72 days
2004	31 days
2005	84 days
2006	43 days
2007	42 days
2008	63 days
2009	67 days
2010	54 days
2011	63 days
2012	40 days
2013	45 days
2014	43 days
2015	19 days
2016	62 days
2017	23 days
2018	36 days
2019	75 days
2020	53 days
2021	21 days
2022	21 days
2023	7 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

62 years, 1960 to 2021

A day with at least 37.0 mm (1.5 in) of rain is expected about once in 2 years. A day with at least 79.7 mm (3.1 in) of rain is expected about once in 100 years.

Rainfall return levels at Copco #1 Dam: the daily rain expected about once in a given number of years
Expected about once in	A day with at least	Note
2 years	37.0 mm (1.5 in)
5 years	49.5 mm (1.9 in)
10 years	57.4 mm (2.3 in)
25 years	66.8 mm (2.6 in)
50 years	73.4 mm (2.9 in)
100 years	79.7 mm (3.1 in)	Longer than the 62 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, 62 years of values from 1960 to 2021.

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: 76.2 mm (3.0 in) in 2008; 74.9 mm (2.9 in) in 1964; 66.0 mm (2.6 in) in 2016.

Download the Data

Data for Copco #1 Dam standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Copco #1 Dam 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 2025-12-31. Last revised 31 December 2025 (2025-12-31).