Bonneville Dam Weather Records (USC00350897)

Record envelope, standing records and threshold days for Bonneville Dam (USC00350897), Oregon, United States, with 90 years of record.

Key Facts for Bonneville Dam

Bonneville Dam (USC00350897) is a weather station in Oregon, United States at 45.64 latitude and -121.95 longitude, 19 m (62 ft) above sea level.
The station reports from 1937 to 2026, 90 years of record.
1,464 records set at Bonneville Dam still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Bonneville Dam set a monthly record high maximum temperature of 30.6 C (87.1 F) on 5 October 2026 (provisional).

Provisional Records

Records set in the last 60 days are provisional until they clear the revision window.

About the Station

Location: Oregon, United States, 45.64 latitude, -121.95 longitude.
Elevation: 19 m (62 ft).
Period of record: 1937 to 2026, 90 years.
Eligible elements: tmax, tmin, prcp, snow, snwd.

Daily Record Envelope and 2026

4 days at or beyond a record

The band shows the record high and record low for each calendar day at Bonneville Dam. The lines show the 2026 daily maximum and minimum. 4 days in 2026 matched or passed a record. Temperatures are in degrees Celsius.

Daily record high and record low at Bonneville Dam, with 2026 drawn through them
Month	Highest record high	Lowest record low	2026 highest maximum	2026 lowest minimum
Jan	17.8 C (64.0 F)	-16.7 C (1.9 F)	12.2 C (54.0 F)	-2.8 C (27.0 F)
Feb	20.0 C (68.0 F)	-13.9 C (7.0 F)	13.9 C (57.0 F)	0.6 C (33.1 F)
Mar	25.0 C (77.0 F)	-6.7 C (19.9 F)	22.2 C (72.0 F)	0.0 C (32.0 F)
Apr	31.1 C (88.0 F)	-2.2 C (28.0 F)	25.0 C (77.0 F)	2.8 C (37.0 F)
May	36.7 C (98.1 F)	-0.6 C (30.9 F)	32.2 C (90.0 F)	7.2 C (45.0 F)
Jun	43.9 C (111.0 F)	2.8 C (37.0 F)	34.4 C (93.9 F)	7.2 C (45.0 F)
Jul	41.7 C (107.1 F)	6.1 C (43.0 F)	36.7 C (98.1 F)	10.6 C (51.1 F)
Aug	41.7 C (107.1 F)	5.6 C (42.1 F)	33.3 C (91.9 F)	10.6 C (51.1 F)
Sep	37.8 C (100.0 F)	1.1 C (34.0 F)	30.6 C (87.1 F)	6.1 C (43.0 F)
Oct	30.0 C (86.0 F)	-1.7 C (28.9 F)	30.6 C (87.1 F)	5.0 C (41.0 F)
Nov	21.7 C (71.1 F)	-12.8 C (9.0 F)	n/a	n/a
Dec	18.3 C (64.9 F)	-17.8 C (0.0 F)	n/a	n/a

Which Years Hold Standing Records

1,464 standing records

1,464 records at Bonneville Dam still stand. 1955 holds the most, with 44.

Standing records at Bonneville Dam by the year they were set
Year set	Standing records
1937	2
1938	15
1939	16
1940	19
1941	24
1942	11
1943	16
1944	16
1945	20
1946	15
1947	16
1948	16
1949	33
1950	38
1951	22
1952	20
1953	20
1954	17
1955	44
1956	16
1957	16
1958	14
1959	9
1960	19
1961	23
1962	9
1963	21
1964	19
1965	17
1966	18
1967	6
1968	20
1969	15
1970	16
1971	25
1972	40
1973	13
1974	13
1975	22
1976	14
1977	18
1978	13
1979	14
1980	16
1981	13
1982	13
1983	18
1984	9
1985	30
1986	19
1987	22
1988	18
1989	14
1990	20
1991	9
1992	19
1993	12
1994	10
1995	10
1996	17
1997	6
1998	19
1999	14
2000	9
2001	6
2002	16
2003	26
2004	10
2005	16
2006	20
2007	10
2008	18
2009	14
2010	7
2011	13
2012	16
2013	6
2014	12
2015	20
2016	17
2017	5
2018	12
2019	20
2020	13
2021	13
2022	17
2023	17
2024	9
2025	19
2026	5

All-Time Record Progression

5 new records

5 all-time records were set at Bonneville Dam between 31 December 1968 and 29 June 2021. Each dot is a new record.

When Bonneville Dam set new all-time records
Date	Kind	Detail
1968-12-31	Record low maximum temperature	Record low maximum temperature -14.4 C (6.1 F)
1968-12-31	Record low minimum temperature	Record low minimum temperature -17.8 C (0.0 F)
1980-01-09	Record daily snowfall	Record daily snowfall 99.1 cm (39.0 in)
2021-06-28	Record high maximum temperature	Record high maximum temperature 42.8 C (109.0 F)
2021-06-29	Record high maximum temperature	Record high maximum temperature 43.9 C (111.0 F)

Wettest Day of Each Month

Dec: 158.2 mm (6.2 in)

The wettest day on record for each calendar month at Bonneville Dam. The most was 158.2 mm (6.2 in) on 27 December 1937.

Record daily precipitation for each month at Bonneville Dam
Month	Record daily precipitation (mm)	Date
Jan	104.6 mm (4.1 in)	15 January 1956
Feb	95.3 mm (3.8 in)	7 February 1996
Mar	101.6 mm (4.0 in)	7 March 1957
Apr	123.2 mm (4.9 in)	10 April 1981
May	59.7 mm (2.4 in)	1 May 2001
Jun	69.6 mm (2.7 in)	8 June 1981
Jul	40.6 mm (1.6 in)	14 July 1983
Aug	52.8 mm (2.1 in)	26 August 1956
Sep	63.0 mm (2.5 in)	30 September 1951
Oct	120.1 mm (4.7 in)	11 October 1959
Nov	129.0 mm (5.1 in)	7 November 2006
Dec	158.2 mm (6.2 in)	27 December 1937

Period of Record Coverage

1937 to 2026

90 years of record at Bonneville Dam, 1937 to 2026. 2 years have data for under 90 percent of days and are left out of rankings: 1937, 2026.

Days with data per year at Bonneville Dam
Year	Days with data	Share of year	Complete
1937	48	13%	No
1938	343	94%	Yes
1939	350	96%	Yes
1940	352	96%	Yes
1941	359	98%	Yes
1942	364	100%	Yes
1943	363	99%	Yes
1944	366	100%	Yes
1945	355	97%	Yes
1946	352	96%	Yes
1947	354	97%	Yes
1948	362	99%	Yes
1949	364	100%	Yes
1950	365	100%	Yes
1951	365	100%	Yes
1952	365	100%	Yes
1953	364	100%	Yes
1954	365	100%	Yes
1955	364	100%	Yes
1956	364	99%	Yes
1957	365	100%	Yes
1958	365	100%	Yes
1959	365	100%	Yes
1960	366	100%	Yes
1961	363	99%	Yes
1962	364	100%	Yes
1963	364	100%	Yes
1964	366	100%	Yes
1965	364	100%	Yes
1966	361	99%	Yes
1967	365	100%	Yes
1968	366	100%	Yes
1969	365	100%	Yes
1970	365	100%	Yes
1971	365	100%	Yes
1972	365	100%	Yes
1973	365	100%	Yes
1974	364	100%	Yes
1975	364	100%	Yes
1976	366	100%	Yes
1977	365	100%	Yes
1978	364	100%	Yes
1979	365	100%	Yes
1980	358	98%	Yes
1981	363	99%	Yes
1982	363	99%	Yes
1983	365	100%	Yes
1984	365	100%	Yes
1985	363	99%	Yes
1986	362	99%	Yes
1987	365	100%	Yes
1988	366	100%	Yes
1989	364	100%	Yes
1990	364	100%	Yes
1991	365	100%	Yes
1992	365	100%	Yes
1993	364	100%	Yes
1994	365	100%	Yes
1995	364	100%	Yes
1996	363	99%	Yes
1997	330	90%	Yes
1998	364	100%	Yes
1999	363	99%	Yes
2000	356	97%	Yes
2001	362	99%	Yes
2002	360	99%	Yes
2003	362	99%	Yes
2004	363	99%	Yes
2005	363	99%	Yes
2006	361	99%	Yes
2007	362	99%	Yes
2008	347	95%	Yes
2009	364	100%	Yes
2010	360	99%	Yes
2011	365	100%	Yes
2012	366	100%	Yes
2013	365	100%	Yes
2014	365	100%	Yes
2015	364	100%	Yes
2016	366	100%	Yes
2017	361	99%	Yes
2018	365	100%	Yes
2019	365	100%	Yes
2020	366	100%	Yes
2021	358	98%	Yes
2022	363	99%	Yes
2023	365	100%	Yes
2024	366	100%	Yes
2025	364	100%	Yes
2026	280	77%	No

Latest Records

Latest records at Bonneville Dam
Date	Station	Record	Value	Beat old record by	Old record stood	Significance
5 October 2026	Bonneville Dam, US	monthly high max (Provisional)	30.6 C (87.1 F)	0.6 C (1.1 F)	74 years	42 of 100 (Notable)
15 June 2026	Bonneville Dam, US	daily high max	33.3 C (91.9 F)	0.5 C (0.9 F)	64 years	29 of 100 (Routine)
15 June 2026	Bonneville Dam, US	daily high min	16.1 C (61.0 F)	0.5 C (0.9 F)	37 years	22 of 100 (Routine)
4 May 2026	Bonneville Dam, US	daily high max	32.2 C (90.0 F)	3.3 C (5.9 F)	8 years	17 of 100 (Routine)
20 March 2026	Bonneville Dam, US	daily high min	8.9 C (48.0 F)	0.6 C (1.1 F)	36 years	21 of 100 (Routine)
17 March 2026	Bonneville Dam, US	daily high max (Tie)	21.7 C (71.1 F)	tie	79 years	8 of 100 (Routine)
14 March 2026	Bonneville Dam, US	daily rain (Tie)	35.6 mm (1.4 in)	tie	64 years	7 of 100 (Routine)
12 March 2026	Bonneville Dam, US	daily rain	56.6 mm (2.2 in)	8.8 mm (0.35 in)	24 years	23 of 100 (Routine)
8 March 2026	Bonneville Dam, US	daily high min	10.0 C (50.0 F)	2.8 C (5.0 F)	84 years	44 of 100 (Notable)
19 December 2025	Bonneville Dam, US	daily rain	130.0 mm (5.1 in)	66.0 mm (2.6 in)	84 years	72 of 100 (Major)
19 December 2025	Bonneville Dam, US	daily high max	16.1 C (61.0 F)	1.1 C (2.0 F)	88 years	36 of 100 (Notable)
17 December 2025	Bonneville Dam, US	daily high max	16.1 C (61.0 F)	0.5 C (0.9 F)	51 years	24 of 100 (Routine)
12 December 2025	Bonneville Dam, US	daily high min	11.1 C (52.0 F)	2.8 C (5.0 F)	68 years	36 of 100 (Notable)
11 December 2025	Bonneville Dam, US	monthly high min	12.8 C (55.0 F)	1.1 C (2.0 F)	50 years	36 of 100 (Notable)
11 December 2025	Bonneville Dam, US	daily high max	17.2 C (63.0 F)	2.2 C (4.0 F)	68 years	33 of 100 (Routine)
10 December 2025	Bonneville Dam, US	daily high min	7.8 C (46.0 F)	1.1 C (2.0 F)	86 years	36 of 100 (Notable)
9 December 2025	Bonneville Dam, US	daily rain	88.9 mm (3.5 in)	7.9 mm (0.31 in)	10 years	15 of 100 (Routine)
8 December 2025	Bonneville Dam, US	daily high min	8.3 C (46.9 F)	0.5 C (0.9 F)	48 years	23 of 100 (Routine)
7 December 2025	Bonneville Dam, US	daily high min (Tie)	7.8 C (46.0 F)	tie	2 years	2 of 100 (Routine)
6 December 2025	Bonneville Dam, US	daily high max	16.1 C (61.0 F)	1.7 C (3.1 F)	80 years	36 of 100 (Notable)

Climate Trend

87 complete years, 1938 to 2025

One stripe for each of 87 complete years at Bonneville Dam, 1938 to 2025. Blue stripes are years cooler than the station's own mean of 11.6 C (52.9 F); red stripes are warmer. The coolest year was 1955, at 9.8 C (49.7 F), and the warmest was 1992, at 13.4 C (56.0 F). The strongest colour marks a difference of 1.8 C (3.2 F).

Annual mean temperature at Bonneville Dam as warming stripes, 1938 to 2025
Year	Annual mean temperature	Difference from the station mean
1938	12.6 C	+0.98 C
1939	12.5 C	+0.89 C
1940	12.7 C	+1.08 C
1941	12.6 C	+0.99 C
1942	11.6 C	-0.03 C
1943	11.0 C	-0.55 C
1944	11.1 C	-0.48 C
1945	11.2 C	-0.39 C
1946	11.2 C	-0.43 C
1947	11.6 C	+0.01 C
1948	10.4 C	-1.16 C
1949	10.6 C	-1.04 C
1950	10.1 C	-1.46 C
1951	11.0 C	-0.58 C
1952	11.2 C	-0.44 C
1953	12.0 C	+0.44 C
1954	10.6 C	-0.95 C
1955	9.8 C	-1.76 C
1956	10.8 C	-0.84 C
1957	10.8 C	-0.75 C
1958	12.6 C	+1.03 C
1959	11.0 C	-0.58 C
1960	10.7 C	-0.85 C
1961	11.7 C	+0.06 C
1962	11.3 C	-0.32 C
1963	11.2 C	-0.44 C
1964	10.7 C	-0.91 C
1965	11.6 C	+0.03 C
1966	11.4 C	-0.21 C
1967	12.5 C	+0.90 C
1968	11.4 C	-0.20 C
1969	11.0 C	-0.55 C
1970	11.1 C	-0.45 C
1971	10.8 C	-0.83 C
1972	11.0 C	-0.64 C
1973	11.3 C	-0.27 C
1974	11.5 C	-0.07 C
1975	11.0 C	-0.61 C
1976	11.4 C	-0.23 C
1977	11.3 C	-0.27 C
1978	11.4 C	-0.18 C
1979	11.3 C	-0.28 C
1980	11.2 C	-0.35 C
1981	12.1 C	+0.49 C
1982	11.3 C	-0.25 C
1983	11.6 C	+0.03 C
1984	11.1 C	-0.50 C
1985	10.4 C	-1.24 C
1986	12.2 C	+0.57 C
1987	12.7 C	+1.15 C
1988	12.3 C	+0.73 C
1989	11.9 C	+0.27 C
1990	12.4 C	+0.78 C
1991	12.1 C	+0.46 C
1992	13.4 C	+1.77 C
1993	11.0 C	-0.55 C
1994	12.3 C	+0.68 C
1995	12.3 C	+0.74 C
1996	11.3 C	-0.32 C
1998	12.2 C	+0.65 C
1999	12.1 C	+0.53 C
2000	11.6 C	+0.02 C
2001	11.8 C	+0.17 C
2002	12.0 C	+0.38 C
2003	12.5 C	+0.90 C
2004	12.7 C	+1.06 C
2005	12.1 C	+0.46 C
2006	12.3 C	+0.66 C
2007	11.7 C	+0.13 C
2008	11.0 C	-0.61 C
2009	11.2 C	-0.44 C
2010	11.4 C	-0.19 C
2011	10.8 C	-0.83 C
2012	11.4 C	-0.18 C
2013	11.5 C	-0.09 C
2014	12.1 C	+0.54 C
2015	13.1 C	+1.52 C
2016	12.3 C	+0.68 C
2017	11.1 C	-0.47 C
2018	12.2 C	+0.61 C
2019	10.9 C	-0.66 C
2020	12.0 C	+0.43 C
2021	12.3 C	+0.72 C
2022	11.4 C	-0.15 C
2023	12.0 C	+0.44 C
2024	11.8 C	+0.20 C
2025	12.6 C	+1.04 C

The annual mean temperature here has risen by 0.09 C (0.03 to 0.14) per decade over 1938 to 2025. In Fahrenheit: 0.2 F (0.1 to 0.3) per decade. The slope is a straight line fitted to 87 complete years; the brackets give its 95 percent interval.

Fitted temperature trends per decade at Bonneville Dam
Measure	Per decade (C)	Per decade (F)	Period	Complete years	Reading
Annual mean temperature	0.09 C (0.03 to 0.14) per decade	0.2 F (0.1 to 0.3) per decade	1938 to 2025	87	Rise
Mean daily maximum	0.11 C (0.04 to 0.17) per decade	0.2 F (0.1 to 0.3) per decade	1938 to 2025	87	Rise
Mean daily minimum	0.07 C (0.01 to 0.12) per decade	0.12 F (0.02 to 0.22) per decade	1938 to 2025	87	Rise

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

1937 to 2026

Yearly extremes at Bonneville Dam: the record and the median year
Measure	Record	Year of the record	Median year	Years with a value
Hottest day (TXx)	43.9 C (111.0 F)	2021	37.2 C (99.0 F)	90
Coldest night (TNn)	-17.8 C (0.0 F)	1968	-7.2 C (19.0 F)	90
Wettest day (Rx1day)	158.2 mm (6.2 in)	1937	79.7 mm (3.1 in)	90
Wettest five days (Rx5day)	328.7 mm (12.9 in)	2006	182.2 mm (7.2 in)	90
Longest dry spell (CDD)	84 days	2012	37 days	90

Hottest day (TXx)

The hottest day of the year at Bonneville Dam, 1937 to 2026. The record is 43.9 C (111.0 F) in 2021, marked on the chart; the median year is 37.2 C (99.0 F).

Hottest day (TXx) at Bonneville Dam by year
Year	Hottest day (TXx)
1937	17.2 C (63.0 F)
1938	40.0 C (104.0 F)
1939	37.2 C (99.0 F)
1940	37.2 C (99.0 F)
1941	41.7 C (107.1 F)
1942	40.6 C (105.1 F)
1943	35.0 C (95.0 F)
1944	37.2 C (99.0 F)
1945	35.6 C (96.1 F)
1946	39.4 C (102.9 F)
1947	34.4 C (93.9 F)
1948	34.4 C (93.9 F)
1949	33.3 C (91.9 F)
1950	34.4 C (93.9 F)
1951	35.6 C (96.1 F)
1952	37.2 C (99.0 F)
1953	38.3 C (100.9 F)
1954	29.4 C (84.9 F)
1955	37.8 C (100.0 F)
1956	39.4 C (102.9 F)
1957	32.2 C (90.0 F)
1958	37.8 C (100.0 F)
1959	35.0 C (95.0 F)
1960	37.8 C (100.0 F)
1961	40.0 C (104.0 F)
1962	32.8 C (91.0 F)
1963	36.7 C (98.1 F)
1964	32.2 C (90.0 F)
1965	38.9 C (102.0 F)
1966	32.2 C (90.0 F)
1967	36.7 C (98.1 F)
1968	36.1 C (97.0 F)
1969	37.2 C (99.0 F)
1970	36.7 C (98.1 F)
1971	35.0 C (95.0 F)
1972	38.9 C (102.0 F)
1973	35.6 C (96.1 F)
1974	33.9 C (93.0 F)
1975	37.8 C (100.0 F)
1976	35.0 C (95.0 F)
1977	41.7 C (107.1 F)
1978	40.6 C (105.1 F)
1979	38.3 C (100.9 F)
1980	37.2 C (99.0 F)
1981	40.6 C (105.1 F)
1982	35.6 C (96.1 F)
1983	36.7 C (98.1 F)
1984	37.2 C (99.0 F)
1985	37.8 C (100.0 F)
1986	37.2 C (99.0 F)
1987	37.8 C (100.0 F)
1988	37.8 C (100.0 F)
1989	35.6 C (96.1 F)
1990	38.3 C (100.9 F)
1991	37.8 C (100.0 F)
1992	38.9 C (102.0 F)
1993	36.1 C (97.0 F)
1994	38.3 C (100.9 F)
1995	35.6 C (96.1 F)
1996	37.2 C (99.0 F)
1997	36.7 C (98.1 F)
1998	37.2 C (99.0 F)
1999	37.2 C (99.0 F)
2000	37.2 C (99.0 F)
2001	38.3 C (100.9 F)
2002	39.4 C (102.9 F)
2003	39.4 C (102.9 F)
2004	38.9 C (102.0 F)
2005	37.2 C (99.0 F)
2006	41.7 C (107.1 F)
2007	40.0 C (104.0 F)
2008	40.6 C (105.1 F)
2009	39.4 C (102.9 F)
2010	36.7 C (98.1 F)
2011	35.0 C (95.0 F)
2012	36.1 C (97.0 F)
2013	35.6 C (96.1 F)
2014	38.9 C (102.0 F)
2015	40.6 C (105.1 F)
2016	38.9 C (102.0 F)
2017	38.9 C (102.0 F)
2018	36.1 C (97.0 F)
2019	35.0 C (95.0 F)
2020	37.2 C (99.0 F)
2021	43.9 C (111.0 F)
2022	37.8 C (100.0 F)
2023	40.0 C (104.0 F)
2024	37.2 C (99.0 F)
2025	38.3 C (100.9 F)
2026	36.7 C (98.1 F)

Coldest night (TNn)

The coldest night of the year at Bonneville Dam, 1937 to 2026. The record is -17.8 C (0.0 F) in 1968, marked on the chart; the median year is -7.2 C (19.0 F).

Coldest night (TNn) at Bonneville Dam by year
Year	Coldest night (TNn)
1937	-1.1 C (30.0 F)
1938	-3.3 C (26.1 F)
1939	-7.2 C (19.0 F)
1940	-5.0 C (23.0 F)
1941	-2.8 C (27.0 F)
1942	-8.9 C (16.0 F)
1943	-13.9 C (7.0 F)
1944	-3.9 C (25.0 F)
1945	-5.0 C (23.0 F)
1946	-3.9 C (25.0 F)
1947	-8.9 C (16.0 F)
1948	-7.8 C (18.0 F)
1949	-14.4 C (6.1 F)
1950	-16.1 C (3.0 F)
1951	-10.0 C (14.0 F)
1952	-11.7 C (10.9 F)
1953	-1.7 C (28.9 F)
1954	-11.7 C (10.9 F)
1955	-10.6 C (12.9 F)
1956	-12.2 C (10.0 F)
1957	-16.7 C (1.9 F)
1958	-2.2 C (28.0 F)
1959	-10.6 C (12.9 F)
1960	-6.7 C (19.9 F)
1961	-7.2 C (19.0 F)
1962	-10.0 C (14.0 F)
1963	-12.2 C (10.0 F)
1964	-15.0 C (5.0 F)
1965	-3.9 C (25.0 F)
1966	-2.2 C (28.0 F)
1967	-11.1 C (12.0 F)
1968	-17.8 C (0.0 F)
1969	-15.0 C (5.0 F)
1970	-5.0 C (23.0 F)
1971	-6.7 C (19.9 F)
1972	-12.8 C (9.0 F)
1973	-7.8 C (18.0 F)
1974	-12.8 C (9.0 F)
1975	-6.7 C (19.9 F)
1976	-3.3 C (26.1 F)
1977	-7.8 C (18.0 F)
1978	-11.1 C (12.0 F)
1979	-13.9 C (7.0 F)
1980	-10.6 C (12.9 F)
1981	-3.3 C (26.1 F)
1982	-11.7 C (10.9 F)
1983	-14.4 C (6.1 F)
1984	-9.4 C (15.1 F)
1985	-12.8 C (9.0 F)
1986	-1.7 C (28.9 F)
1987	-3.9 C (25.0 F)
1988	-6.1 C (21.0 F)
1989	-13.3 C (8.1 F)
1990	-12.8 C (9.0 F)
1991	-4.4 C (24.1 F)
1992	-3.3 C (26.1 F)
1993	-6.7 C (19.9 F)
1994	-5.6 C (21.9 F)
1995	-5.0 C (23.0 F)
1996	-13.9 C (7.0 F)
1997	-3.9 C (25.0 F)
1998	-9.4 C (15.1 F)
1999	-2.2 C (28.0 F)
2000	-3.3 C (26.1 F)
2001	-2.2 C (28.0 F)
2002	-2.8 C (27.0 F)
2003	-3.3 C (26.1 F)
2004	-11.1 C (12.0 F)
2005	-5.6 C (21.9 F)
2006	-6.7 C (19.9 F)
2007	-7.2 C (19.0 F)
2008	-10.6 C (12.9 F)
2009	-9.4 C (15.1 F)
2010	-7.8 C (18.0 F)
2011	-8.3 C (17.1 F)
2012	-5.6 C (21.9 F)
2013	-11.1 C (12.0 F)
2014	-10.0 C (14.0 F)
2015	-5.6 C (21.9 F)
2016	-5.6 C (21.9 F)
2017	-9.4 C (15.1 F)
2018	-7.2 C (19.0 F)
2019	-6.1 C (21.0 F)
2020	-2.2 C (28.0 F)
2021	-6.7 C (19.9 F)
2022	-10.6 C (12.9 F)
2023	-6.7 C (19.9 F)
2024	-12.8 C (9.0 F)
2025	-5.6 C (21.9 F)
2026	-2.8 C (27.0 F)

Wettest day (Rx1day)

The wettest day of the year at Bonneville Dam, 1937 to 2026. The record is 158.2 mm (6.2 in) in 1937, marked on the chart; the median year is 79.7 mm (3.1 in).

Wettest day (Rx1day) at Bonneville Dam by year
Year	Wettest day (Rx1day)
1937	158.2 mm (6.2 in)
1938	64.3 mm (2.5 in)
1939	62.2 mm (2.4 in)
1940	92.7 mm (3.6 in)
1941	77.5 mm (3.1 in)
1942	79.5 mm (3.1 in)
1943	67.8 mm (2.7 in)
1944	48.3 mm (1.9 in)
1945	128.3 mm (5.1 in)
1946	88.9 mm (3.5 in)
1947	66.0 mm (2.6 in)
1948	96.5 mm (3.8 in)
1949	86.1 mm (3.4 in)
1950	67.8 mm (2.7 in)
1951	80.0 mm (3.1 in)
1952	60.7 mm (2.4 in)
1953	88.4 mm (3.5 in)
1954	72.1 mm (2.8 in)
1955	78.7 mm (3.1 in)
1956	104.6 mm (4.1 in)
1957	101.6 mm (4.0 in)
1958	94.0 mm (3.7 in)
1959	120.1 mm (4.7 in)
1960	73.7 mm (2.9 in)
1961	89.9 mm (3.5 in)
1962	75.7 mm (3.0 in)
1963	68.6 mm (2.7 in)
1964	102.1 mm (4.0 in)
1965	57.2 mm (2.3 in)
1966	62.2 mm (2.4 in)
1967	54.1 mm (2.1 in)
1968	76.2 mm (3.0 in)
1969	78.5 mm (3.1 in)
1970	82.8 mm (3.3 in)
1971	64.3 mm (2.5 in)
1972	70.1 mm (2.8 in)
1973	61.0 mm (2.4 in)
1974	71.1 mm (2.8 in)
1975	91.9 mm (3.6 in)
1976	56.4 mm (2.2 in)
1977	81.3 mm (3.2 in)
1978	62.0 mm (2.4 in)
1979	79.8 mm (3.1 in)
1980	89.4 mm (3.5 in)
1981	123.2 mm (4.9 in)
1982	65.3 mm (2.6 in)
1983	58.9 mm (2.3 in)
1984	53.8 mm (2.1 in)
1985	64.3 mm (2.5 in)
1986	81.5 mm (3.2 in)
1987	85.6 mm (3.4 in)
1988	52.1 mm (2.1 in)
1989	67.1 mm (2.6 in)
1990	64.3 mm (2.5 in)
1991	65.5 mm (2.6 in)
1992	89.9 mm (3.5 in)
1993	70.1 mm (2.8 in)
1994	113.5 mm (4.5 in)
1995	94.0 mm (3.7 in)
1996	109.5 mm (4.3 in)
1997	86.4 mm (3.4 in)
1998	87.9 mm (3.5 in)
1999	128.3 mm (5.1 in)
2000	103.6 mm (4.1 in)
2001	87.6 mm (3.4 in)
2002	50.8 mm (2.0 in)
2003	68.6 mm (2.7 in)
2004	54.9 mm (2.2 in)
2005	95.3 mm (3.8 in)
2006	129.0 mm (5.1 in)
2007	97.0 mm (3.8 in)
2008	67.3 mm (2.6 in)
2009	103.4 mm (4.1 in)
2010	74.9 mm (2.9 in)
2011	80.0 mm (3.1 in)
2012	75.2 mm (3.0 in)
2013	119.6 mm (4.7 in)
2014	87.4 mm (3.4 in)
2015	88.6 mm (3.5 in)
2016	90.4 mm (3.6 in)
2017	116.3 mm (4.6 in)
2018	52.6 mm (2.1 in)
2019	58.9 mm (2.3 in)
2020	60.7 mm (2.4 in)
2021	95.8 mm (3.8 in)
2022	108.0 mm (4.3 in)
2023	97.0 mm (3.8 in)
2024	67.3 mm (2.6 in)
2025	130.0 mm (5.1 in)
2026	56.6 mm (2.2 in)

Wettest five days (Rx5day)

The wettest five days of the year at Bonneville Dam, 1937 to 2026. The record is 328.7 mm (12.9 in) in 2006, marked on the chart; the median year is 182.2 mm (7.2 in).

Wettest five days (Rx5day) at Bonneville Dam by year
Year	Wettest five days (Rx5day)
1937	270.3 mm (10.6 in)
1938	153.7 mm (6.1 in)
1939	137.9 mm (5.4 in)
1940	162.1 mm (6.4 in)
1941	176.3 mm (6.9 in)
1942	216.2 mm (8.5 in)
1943	209.9 mm (8.3 in)
1944	97.8 mm (3.9 in)
1945	180.6 mm (7.1 in)
1946	244.4 mm (9.6 in)
1947	240.2 mm (9.5 in)
1948	197.6 mm (7.8 in)
1949	223.3 mm (8.8 in)
1950	178.6 mm (7.0 in)
1951	174.7 mm (6.9 in)
1952	144.8 mm (5.7 in)
1953	225.9 mm (8.9 in)
1954	138.0 mm (5.4 in)
1955	167.4 mm (6.6 in)
1956	190.8 mm (7.5 in)
1957	193.1 mm (7.6 in)
1958	187.7 mm (7.4 in)
1959	179.3 mm (7.1 in)
1960	220.8 mm (8.7 in)
1961	190.5 mm (7.5 in)
1962	122.0 mm (4.8 in)
1963	132.9 mm (5.2 in)
1964	293.7 mm (11.6 in)
1965	183.1 mm (7.2 in)
1966	171.4 mm (6.7 in)
1967	139.9 mm (5.5 in)
1968	201.5 mm (7.9 in)
1969	221.0 mm (8.7 in)
1970	223.3 mm (8.8 in)
1971	176.8 mm (7.0 in)
1972	181.7 mm (7.2 in)
1973	173.3 mm (6.8 in)
1974	212.1 mm (8.4 in)
1975	176.0 mm (6.9 in)
1976	153.3 mm (6.0 in)
1977	239.2 mm (9.4 in)
1978	113.1 mm (4.5 in)
1979	141.2 mm (5.6 in)
1980	247.3 mm (9.7 in)
1981	188.8 mm (7.4 in)
1982	179.0 mm (7.0 in)
1983	230.8 mm (9.1 in)
1984	145.3 mm (5.7 in)
1985	132.9 mm (5.2 in)
1986	199.0 mm (7.8 in)
1987	174.0 mm (6.9 in)
1988	175.2 mm (6.9 in)
1989	122.5 mm (4.8 in)
1990	226.6 mm (8.9 in)
1991	161.0 mm (6.3 in)
1992	172.6 mm (6.8 in)
1993	144.3 mm (5.7 in)
1994	227.6 mm (9.0 in)
1995	209.6 mm (8.3 in)
1996	322.9 mm (12.7 in)
1997	257.0 mm (10.1 in)
1998	217.4 mm (8.6 in)
1999	260.1 mm (10.2 in)
2000	160.3 mm (6.3 in)
2001	209.0 mm (8.2 in)
2002	150.7 mm (5.9 in)
2003	176.9 mm (7.0 in)
2004	126.5 mm (5.0 in)
2005	208.1 mm (8.2 in)
2006	328.7 mm (12.9 in)
2007	182.1 mm (7.2 in)
2008	138.6 mm (5.5 in)
2009	187.8 mm (7.4 in)
2010	195.5 mm (7.7 in)
2011	209.3 mm (8.2 in)
2012	222.3 mm (8.8 in)
2013	166.3 mm (6.5 in)
2014	149.0 mm (5.9 in)
2015	239.0 mm (9.4 in)
2016	182.3 mm (7.2 in)
2017	198.8 mm (7.8 in)
2018	102.3 mm (4.0 in)
2019	153.3 mm (6.0 in)
2020	127.8 mm (5.0 in)
2021	199.2 mm (7.8 in)
2022	199.7 mm (7.9 in)
2023	258.0 mm (10.2 in)
2024	153.1 mm (6.0 in)
2025	234.4 mm (9.2 in)
2026	159.7 mm (6.3 in)

Longest dry spell (CDD)

The longest dry spell of the year at Bonneville Dam, 1937 to 2026. The record is 84 days in 2012, marked on the chart; the median year is 37 days.

Longest dry spell (CDD) at Bonneville Dam by year
Year	Longest dry spell (CDD)
1937	8 days
1938	57 days
1939	39 days
1940	48 days
1941	39 days
1942	32 days
1943	27 days
1944	59 days
1945	37 days
1946	45 days
1947	26 days
1948	19 days
1949	19 days
1950	31 days
1951	52 days
1952	55 days
1953	28 days
1954	28 days
1955	47 days
1956	42 days
1957	40 days
1958	58 days
1959	50 days
1960	55 days
1961	39 days
1962	28 days
1963	24 days
1964	18 days
1965	25 days
1966	18 days
1967	72 days
1968	24 days
1969	24 days
1970	37 days
1971	41 days
1972	34 days
1973	51 days
1974	21 days
1975	36 days
1976	25 days
1977	42 days
1978	18 days
1979	33 days
1980	33 days
1981	47 days
1982	26 days
1983	17 days
1984	61 days
1985	51 days
1986	42 days
1987	34 days
1988	32 days
1989	27 days
1990	24 days
1991	32 days
1992	31 days
1993	43 days
1994	36 days
1995	23 days
1996	28 days
1997	44 days
1998	48 days
1999	23 days
2000	45 days
2001	32 days
2002	56 days
2003	31 days
2004	52 days
2005	37 days
2006	31 days
2007	28 days
2008	48 days
2009	29 days
2010	59 days
2011	28 days
2012	84 days
2013	43 days
2014	37 days
2015	52 days
2016	52 days
2017	56 days
2018	70 days
2019	22 days
2020	29 days
2021	50 days
2022	68 days
2023	70 days
2024	32 days
2025	44 days
2026	65 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

86 years with a frost

Across 86 years with a frost, the median last spring frost at Bonneville Dam falls on 20 March and the median first autumn frost on 22 November, which leaves a median of 246 days between them.

In 1995 to 2025 the median growing season was 247 days. That is 5 days more than in 1938 to 1967.

Fitted over all years, the growing season changes by +2.8 days per decade at this station.

Frost dates and growing season at Bonneville Dam
Measure	Median, all years	Earliest period (1938 to 1967)	Recent period (1995 to 2025)	Recent against earliest	Fitted trend
Last spring frost	20 March	28 March	20 March	8 days earlier	-1.8 days per decade
First autumn frost	22 November	20 November	24 November	4 days later	+1.0 days per decade
Growing days	246 days	242 days	247 days	5 days more	+2.8 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

88 years, 1938 to 2025

A day with at least 78.9 mm (3.1 in) of rain is expected about once in 2 years. A day with at least 143.7 mm (5.7 in) of rain is expected about once in 100 years.

Rainfall return levels at Bonneville 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	78.9 mm (3.1 in)
5 years	97.8 mm (3.9 in)
10 years	109.7 mm (4.3 in)
25 years	124.0 mm (4.9 in)
50 years	134.1 mm (5.3 in)
100 years	143.7 mm (5.7 in)	Longer than the 88 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, 88 years of values from 1938 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: 130.0 mm (5.1 in) in 2025; 129.0 mm (5.1 in) in 2006; 128.3 mm (5.1 in) in 1945.

Station Changes

No change in the annual mean temperature of this station was found against its neighbours.

Climate Twins

2011 to 2025 against 1961 to 1990

Over 2011 to 2025, Bonneville Dam had a mean temperature of 11.8 C (53.3 F) and 2,023.9 mm (79.7 in) of rain a year. The 3 stations whose 1961 to 1990 climate was closest to that are Strawberry Valley 2 (United States, 682 km away), Krasnaja Poljana (Russia, 9,937 km away) and Highlands (United States, 3,449 km away).

Climate twins of Bonneville Dam: stations whose 1961 to 1990 climate is closest to its 2011 to 2025 climate
Twin station	Country	Distance away	Mean temperature, 1961-1990	Rain a year, 1961-1990	Climate difference
Strawberry Valley 2	United States	682 km (424 mi)	10.9 C (51.7 F)	1,985.4 mm (78.2 in)	1.30
Krasnaja Poljana	Russia	9,937 km (6,175 mi)	11.0 C (51.8 F)	1,948.6 mm (76.7 in)	1.30
Highlands	United States	3,449 km (2,143 mi)	11.0 C (51.7 F)	2,050.1 mm (80.7 in)	1.45

Twins are stations, not cities. A twin is one of the three stations at least 100 km away whose earlier climate is closest to this station's recent one, so a close match does not mean the two places look alike in other ways. A station move or a gap in a record can change that station's averages. The list describes past climate; it is not a forecast and does not say what caused any change. How twins are found, and a search for any station.

Download the Data

Data for Bonneville Dam standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Bonneville 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 2026-10-13 (13 October 2026). Records are computed by this site and are not official.

Data as of 2026-10-13. Last revised 13 October 2026 (2026-10-13).