Boulder Weather Records (USC00241008)

Record envelope, standing records and threshold days for Boulder (USC00241008), Montana, United States, with 147 years of record.

Key Facts for Boulder

Boulder (USC00241008) is a weather station in Montana, United States at 46.23 latitude and -112.11 longitude, 1,495 m (4,904 ft) above sea level.
The station reports from 1880 to 2026, 147 years of record.
1,464 records set at Boulder still stand.
Records are tracked for tmax, tmin, prcp, snow, snwd: an element needs 30 years of data to be eligible.
Boulder tied a daily record high maximum temperature of 27.8 C (82.0 F) on 11 October 2026 (provisional).

Provisional Records

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

About the Station

Location: Montana, United States, 46.23 latitude, -112.11 longitude.
Elevation: 1,495 m (4,904 ft).
Period of record: 1880 to 2026, 147 years.
Eligible elements: tmax, tmin, prcp, snow, snwd.

Daily Record Envelope and 2026

12 days at or beyond a record

The band shows the record high and record low for each calendar day at Boulder. The lines show the 2026 daily maximum and minimum. 12 days in 2026 matched or passed a record. Temperatures are in degrees Celsius.

Daily record high and record low at Boulder, with 2026 drawn through them
Month	Highest record high	Lowest record low	2026 highest maximum	2026 lowest minimum
Jan	15.0 C (59.0 F)	-38.9 C (-38.0 F)	15.0 C (59.0 F)	-21.7 C (-7.1 F)
Feb	18.3 C (64.9 F)	-39.4 C (-38.9 F)	16.1 C (61.0 F)	-24.4 C (-11.9 F)
Mar	23.3 C (73.9 F)	-36.7 C (-34.1 F)	23.3 C (73.9 F)	-14.4 C (6.1 F)
Apr	28.3 C (82.9 F)	-21.1 C (-6.0 F)	24.4 C (75.9 F)	-8.3 C (17.1 F)
May	31.7 C (89.1 F)	-12.8 C (9.0 F)	28.9 C (84.0 F)	-7.2 C (19.0 F)
Jun	35.6 C (96.1 F)	-5.6 C (21.9 F)	28.3 C (82.9 F)	-3.3 C (26.1 F)
Jul	38.3 C (100.9 F)	-1.7 C (28.9 F)	36.7 C (98.1 F)	6.1 C (43.0 F)
Aug	37.8 C (100.0 F)	-7.2 C (19.0 F)	36.1 C (97.0 F)	2.8 C (37.0 F)
Sep	35.6 C (96.1 F)	-13.3 C (8.1 F)	27.2 C (81.0 F)	-2.8 C (27.0 F)
Oct	30.6 C (87.1 F)	-25.6 C (-14.1 F)	27.8 C (82.0 F)	-2.2 C (28.0 F)
Nov	21.7 C (71.1 F)	-36.7 C (-34.1 F)	n/a	n/a
Dec	18.3 C (64.9 F)	-41.1 C (-42.0 F)	n/a	n/a

Which Years Hold Standing Records

1,464 standing records

1,464 records at Boulder still stand. 1985 holds the most, with 37.

Standing records at Boulder by the year they were set
Year set	Standing records
1948	10
1949	29
1950	32
1951	27
1952	12
1953	17
1954	30
1955	33
1956	14
1957	16
1958	12
1959	15
1960	23
1961	20
1962	26
1963	22
1964	13
1965	21
1966	26
1967	17
1968	10
1969	26
1970	13
1971	20
1972	34
1973	17
1974	20
1975	22
1976	5
1977	20
1978	19
1979	17
1980	18
1981	16
1982	10
1983	25
1984	23
1985	37
1986	23
1987	19
1988	27
1989	31
1990	25
1991	12
1992	25
1993	24
1994	21
1995	18
1996	26
1997	13
1998	6
1999	21
2000	13
2001	10
2002	29
2003	29
2004	16
2005	17
2006	22
2007	18
2008	14
2009	17
2010	12
2011	11
2012	16
2013	12
2014	12
2015	26
2016	8
2017	11
2018	4
2019	6
2020	13
2021	16
2022	22
2023	10
2024	15
2025	15
2026	12

All-Time Record Progression

9 new records

9 all-time records were set at Boulder between 24 May 1981 and 1 March 2014. Each dot is a new record.

When Boulder set new all-time records
Date	Kind	Detail
1981-05-24	Record daily precipitation	Record daily precipitation 43.2 mm (1.7 in)
1983-07-10	Record daily precipitation	Record daily precipitation 47.0 mm (1.9 in)
1983-12-23	Record low minimum temperature	Record low minimum temperature -39.4 C (-38.9 F)
1983-12-24	Record low minimum temperature	Record low minimum temperature -40.0 C (-40.0 F)
1989-02-02	Record low maximum temperature	Record low maximum temperature -32.2 C (-26.0 F)
1990-12-22	Record low minimum temperature	Record low minimum temperature -41.1 C (-42.0 F)
2001-08-08	Record high minimum temperature	Record high minimum temperature 18.9 C (66.0 F)
2002-07-14	Record high maximum temperature	Record high maximum temperature 38.3 C (100.9 F)
2014-03-01	Record snow depth	Record snow depth 58.4 cm (23.0 in)

Wettest Day of Each Month

Jul: 47.0 mm (1.9 in)

The wettest day on record for each calendar month at Boulder. The most was 47.0 mm (1.9 in) on 10 July 1983.

Record daily precipitation for each month at Boulder
Month	Record daily precipitation (mm)	Date
Jan	15.2 mm (0.6 in)	26 January 1975
Feb	15.2 mm (0.6 in)	17 February 1986
Mar	13.2 mm (0.5 in)	16 March 1965
Apr	34.8 mm (1.4 in)	26 April 1955
May	43.2 mm (1.7 in)	24 May 1981
Jun	38.9 mm (1.5 in)	10 June 2006
Jul	47.0 mm (1.9 in)	10 July 1983
Aug	39.4 mm (1.6 in)	7 August 2023
Sep	30.0 mm (1.2 in)	8 September 1995
Oct	30.5 mm (1.2 in)	18 October 2020
Nov	26.7 mm (1.1 in)	29 November 1971
Dec	15.7 mm (0.6 in)	3 December 1948

Period of Record Coverage

1880 to 2026

80 years of record at Boulder, 1880 to 2026. 12 years have data for under 90 percent of days and are left out of rankings: 1880, 1948, 1965, 1968, 2018, 2019, 2020, 2021 and others.

Days with data per year at Boulder
Year	Days with data	Share of year	Complete
1880	1	0%	No
1948	184	50%	No
1949	361	99%	Yes
1950	359	98%	Yes
1951	363	99%	Yes
1952	366	100%	Yes
1953	360	99%	Yes
1954	365	100%	Yes
1955	360	99%	Yes
1956	365	100%	Yes
1957	364	100%	Yes
1958	363	99%	Yes
1959	363	99%	Yes
1960	366	100%	Yes
1961	361	99%	Yes
1962	363	99%	Yes
1963	361	99%	Yes
1964	334	91%	Yes
1965	296	81%	No
1966	360	99%	Yes
1967	365	100%	Yes
1968	302	83%	No
1969	361	99%	Yes
1970	361	99%	Yes
1971	365	100%	Yes
1972	363	99%	Yes
1973	359	98%	Yes
1974	364	100%	Yes
1975	363	99%	Yes
1976	365	100%	Yes
1977	362	99%	Yes
1978	362	99%	Yes
1979	361	99%	Yes
1980	360	98%	Yes
1981	359	98%	Yes
1982	359	98%	Yes
1983	354	97%	Yes
1984	364	99%	Yes
1985	361	99%	Yes
1986	361	99%	Yes
1987	348	95%	Yes
1988	354	97%	Yes
1989	357	98%	Yes
1990	350	96%	Yes
1991	351	96%	Yes
1992	359	98%	Yes
1993	358	98%	Yes
1994	357	98%	Yes
1995	360	99%	Yes
1996	360	98%	Yes
1997	350	96%	Yes
1998	360	99%	Yes
1999	360	99%	Yes
2000	356	97%	Yes
2001	358	98%	Yes
2002	360	99%	Yes
2003	350	96%	Yes
2004	349	95%	Yes
2005	350	96%	Yes
2006	363	99%	Yes
2007	356	98%	Yes
2008	359	98%	Yes
2009	361	99%	Yes
2010	346	95%	Yes
2011	332	91%	Yes
2012	334	91%	Yes
2013	349	96%	Yes
2014	353	97%	Yes
2015	342	94%	Yes
2016	340	93%	Yes
2017	346	95%	Yes
2018	197	54%	No
2019	158	43%	No
2020	243	66%	No
2021	191	52%	No
2022	293	80%	No
2023	282	77%	No
2024	336	92%	Yes
2025	231	63%	No
2026	128	35%	No

Latest Records

Latest records at Boulder
Date	Station	Record	Value	Beat old record by	Old record stood	Significance
11 October 2026	Boulder, US	daily high max (Tie, Provisional)	27.8 C (82.0 F)	tie	11 years	3 of 100 (Routine)
2 August 2026	Boulder, US	daily high max (Tie)	36.1 C (97.0 F)	tie	73 years	8 of 100 (Routine)
29 June 2026	Boulder, US	daily low max	12.2 C (54.0 F)	2.2 C (4.0 F)	56 years	31 of 100 (Routine)
21 June 2026	Boulder, US	daily low min	0.0 C (32.0 F)	0.6 C (1.1 F)	72 years	32 of 100 (Routine)
8 June 2026	Boulder, US	daily low min	-3.3 C (26.1 F)	1.6 C (2.9 F)	76 years	36 of 100 (Notable)
19 May 2026	Boulder, US	daily low min	-6.7 C (19.9 F)	0.6 C (1.1 F)	28 years	19 of 100 (Routine)
17 May 2026	Boulder, US	daily low min	-6.1 C (21.0 F)	2.2 C (4.0 F)	40 years	27 of 100 (Routine)
13 May 2026	Boulder, US	daily high max	28.9 C (84.0 F)	0.6 C (1.1 F)	12 years	14 of 100 (Routine)
25 March 2026	Boulder, US	monthly high min	8.9 C (48.0 F)	2.8 C (5.0 F)	57 years	41 of 100 (Notable)
22 March 2026	Boulder, US	monthly high max	23.3 C (73.9 F)	1.1 C (2.0 F)	47 years	35 of 100 (Notable)
5 March 2026	Boulder, US	daily high min (Tie)	0.6 C (33.1 F)	tie	39 years	5 of 100 (Routine)
9 February 2026	Boulder, US	daily high max	16.1 C (61.0 F)	1.7 C (3.1 F)	11 years	15 of 100 (Routine)
18 January 2026	Boulder, US	monthly high max	15.0 C (59.0 F)	0.6 C (1.1 F)	57 years	37 of 100 (Notable)
14 January 2026	Boulder, US	monthly high max (Tie)	14.4 C (57.9 F)	tie	57 years	9 of 100 (Routine)
13 January 2026	Boulder, US	daily high max	12.8 C (55.0 F)	0.6 C (1.1 F)	30 years	19 of 100 (Routine)
28 December 2025	Boulder, US	daily high max (Tie)	11.7 C (53.1 F)	tie	68 years	7 of 100 (Routine)
24 December 2025	Boulder, US	daily high max	11.7 C (53.1 F)	2.3 C (4.1 F)	71 years	34 of 100 (Routine)
15 December 2025	Boulder, US	daily high max	16.1 C (61.0 F)	0.5 C (0.9 F)	44 years	23 of 100 (Routine)
14 December 2025	Boulder, US	daily high max	15.6 C (60.1 F)	5.0 C (9.0 F)	63 years	35 of 100 (Notable)
9 December 2025	Boulder, US	daily high min	2.8 C (37.0 F)	0.6 C (1.1 F)	10 years	13 of 100 (Routine)

Climate Trend

64 complete years, 1949 to 2024

One stripe for each of 64 complete years at Boulder, 1949 to 2024. Blue stripes are years cooler than the station's own mean of 5.9 C (42.7 F); red stripes are warmer. The coolest year was 1993, at 4.2 C (39.6 F), and the warmest was 2012, at 7.4 C (45.3 F). The strongest colour marks a difference of 1.8 C (3.2 F).

Annual mean temperature at Boulder as warming stripes, 1949 to 2024
Year	Annual mean temperature	Difference from the station mean
1949	5.3 C	-0.66 C
1951	4.2 C	-1.71 C
1952	5.1 C	-0.83 C
1953	6.7 C	+0.79 C
1956	5.6 C	-0.32 C
1957	5.4 C	-0.50 C
1958	6.3 C	+0.41 C
1959	5.4 C	-0.58 C
1960	5.0 C	-0.94 C
1961	6.5 C	+0.54 C
1962	5.3 C	-0.66 C
1963	6.2 C	+0.29 C
1966	6.0 C	+0.10 C
1967	5.9 C	-0.05 C
1969	4.9 C	-0.99 C
1970	5.6 C	-0.32 C
1971	5.7 C	-0.20 C
1972	5.4 C	-0.50 C
1973	6.0 C	+0.03 C
1974	6.7 C	+0.74 C
1975	4.6 C	-1.38 C
1976	6.7 C	+0.76 C
1977	6.2 C	+0.22 C
1978	5.2 C	-0.71 C
1979	5.5 C	-0.42 C
1980	6.1 C	+0.12 C
1981	6.9 C	+0.92 C
1982	4.7 C	-1.24 C
1983	5.9 C	-0.02 C
1984	5.7 C	-0.22 C
1985	4.4 C	-1.50 C
1986	6.5 C	+0.61 C
1987	6.9 C	+0.92 C
1988	7.1 C	+1.21 C
1989	5.2 C	-0.72 C
1990	6.5 C	+0.59 C
1991	6.5 C	+0.52 C
1992	6.6 C	+0.66 C
1993	4.2 C	-1.73 C
1994	5.9 C	+0.01 C
1995	5.4 C	-0.58 C
1996	4.7 C	-1.25 C
1997	5.7 C	-0.23 C
1998	6.6 C	+0.65 C
1999	6.7 C	+0.77 C
2000	6.0 C	+0.04 C
2001	6.5 C	+0.56 C
2002	5.4 C	-0.50 C
2003	6.7 C	+0.78 C
2004	6.4 C	+0.46 C
2005	5.9 C	+0.00 C
2006	7.0 C	+1.02 C
2007	7.1 C	+1.15 C
2008	5.6 C	-0.35 C
2009	5.5 C	-0.46 C
2010	5.3 C	-0.60 C
2011	5.7 C	-0.24 C
2012	7.4 C	+1.47 C
2013	6.7 C	+0.77 C
2014	5.9 C	-0.01 C
2015	7.4 C	+1.44 C
2016	6.6 C	+0.67 C
2017	6.1 C	+0.18 C
2024	6.9 C	+0.98 C

The annual mean temperature here has risen by 0.1 C (0.1 to 0.2) per decade over 1949 to 2024. In Fahrenheit: 0.3 F (0.1 to 0.4) per decade. The slope is a straight line fitted to 64 complete years; the brackets give its 95 percent interval.

Fitted temperature trends per decade at Boulder
Measure	Per decade (C)	Per decade (F)	Period	Complete years	Reading
Annual mean temperature	0.1 C (0.1 to 0.2) per decade	0.3 F (0.1 to 0.4) per decade	1949 to 2024	64	Rise
Mean daily maximum	0.12 C (0.01 to 0.23) per decade	0.21 F (0.01 to 0.41) per decade	1949 to 2024	64	Rise
Mean daily minimum	0.2 C (0.1 to 0.3) per decade	0.3 F (0.1 to 0.5) per decade	1949 to 2024	64	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

1880 to 2026

Yearly extremes at Boulder: the record and the median year
Measure	Record	Year of the record	Median year	Years with a value
Hottest day (TXx)	38.3 C (100.9 F)	2002	34.4 C (93.9 F)	80
Coldest night (TNn)	-41.1 C (-42.0 F)	1990	-32.2 C (-26.0 F)	80
Wettest day (Rx1day)	47.0 mm (1.9 in)	1983	21.6 mm (0.9 in)	80
Wettest five days (Rx5day)	74.0 mm (2.9 in)	2006	36.1 mm (1.4 in)	79
Longest dry spell (CDD)	82 days	1999	33 days	80

Hottest day (TXx)

The hottest day of the year at Boulder, 1880 to 2026. The record is 38.3 C (100.9 F) in 2002, marked on the chart; the median year is 34.4 C (93.9 F).

Hottest day (TXx) at Boulder by year
Year	Hottest day (TXx)
1880	23.9 C (75.0 F)
1948	32.2 C (90.0 F)
1949	35.6 C (96.1 F)
1950	34.4 C (93.9 F)
1951	36.7 C (98.1 F)
1952	36.1 C (97.0 F)
1953	37.2 C (99.0 F)
1954	36.1 C (97.0 F)
1955	35.6 C (96.1 F)
1956	34.4 C (93.9 F)
1957	33.9 C (93.0 F)
1958	33.3 C (91.9 F)
1959	34.4 C (93.9 F)
1960	37.2 C (99.0 F)
1961	37.8 C (100.0 F)
1962	32.8 C (91.0 F)
1963	34.4 C (93.9 F)
1964	33.9 C (93.0 F)
1965	32.2 C (90.0 F)
1966	36.1 C (97.0 F)
1967	33.9 C (93.0 F)
1968	33.3 C (91.9 F)
1969	36.1 C (97.0 F)
1970	34.4 C (93.9 F)
1971	37.2 C (99.0 F)
1972	34.4 C (93.9 F)
1973	35.6 C (96.1 F)
1974	35.0 C (95.0 F)
1975	34.4 C (93.9 F)
1976	32.8 C (91.0 F)
1977	32.8 C (91.0 F)
1978	33.9 C (93.0 F)
1979	35.6 C (96.1 F)
1980	33.9 C (93.0 F)
1981	35.6 C (96.1 F)
1982	33.3 C (91.9 F)
1983	36.1 C (97.0 F)
1984	34.4 C (93.9 F)
1985	35.6 C (96.1 F)
1986	35.0 C (95.0 F)
1987	32.8 C (91.0 F)
1988	35.6 C (96.1 F)
1989	35.0 C (95.0 F)
1990	35.6 C (96.1 F)
1991	36.1 C (97.0 F)
1992	33.3 C (91.9 F)
1993	31.7 C (89.1 F)
1994	33.9 C (93.0 F)
1995	33.9 C (93.0 F)
1996	33.9 C (93.0 F)
1997	31.7 C (89.1 F)
1998	35.0 C (95.0 F)
1999	34.4 C (93.9 F)
2000	35.6 C (96.1 F)
2001	34.4 C (93.9 F)
2002	38.3 C (100.9 F)
2003	35.6 C (96.1 F)
2004	33.9 C (93.0 F)
2005	34.4 C (93.9 F)
2006	36.1 C (97.0 F)
2007	37.2 C (99.0 F)
2008	33.3 C (91.9 F)
2009	33.3 C (91.9 F)
2010	33.9 C (93.0 F)
2011	33.3 C (91.9 F)
2012	33.9 C (93.0 F)
2013	35.0 C (95.0 F)
2014	32.2 C (90.0 F)
2015	35.0 C (95.0 F)
2016	33.3 C (91.9 F)
2017	35.0 C (95.0 F)
2018	33.9 C (93.0 F)
2019	32.2 C (90.0 F)
2020	35.0 C (95.0 F)
2021	35.6 C (96.1 F)
2022	35.6 C (96.1 F)
2023	35.0 C (95.0 F)
2024	35.6 C (96.1 F)
2025	33.9 C (93.0 F)
2026	36.7 C (98.1 F)

Coldest night (TNn)

The coldest night of the year at Boulder, 1880 to 2026. The record is -41.1 C (-42.0 F) in 1990, marked on the chart; the median year is -32.2 C (-26.0 F).

Coldest night (TNn) at Boulder by year
Year	Coldest night (TNn)
1880	7.2 C (45.0 F)
1948	-31.1 C (-24.0 F)
1949	-37.2 C (-35.0 F)
1950	-34.4 C (-29.9 F)
1951	-33.9 C (-29.0 F)
1952	-32.2 C (-26.0 F)
1953	-23.3 C (-9.9 F)
1954	-38.3 C (-36.9 F)
1955	-32.2 C (-26.0 F)
1956	-37.2 C (-35.0 F)
1957	-38.9 C (-38.0 F)
1958	-25.0 C (-13.0 F)
1959	-36.7 C (-34.1 F)
1960	-30.0 C (-22.0 F)
1961	-32.8 C (-27.0 F)
1962	-36.7 C (-34.1 F)
1963	-37.8 C (-36.0 F)
1964	-38.3 C (-36.9 F)
1965	-28.3 C (-18.9 F)
1966	-26.7 C (-16.1 F)
1967	-32.2 C (-26.0 F)
1968	-35.6 C (-32.1 F)
1969	-36.1 C (-33.0 F)
1970	-30.6 C (-23.1 F)
1971	-32.2 C (-26.0 F)
1972	-37.2 C (-35.0 F)
1973	-34.4 C (-29.9 F)
1974	-32.8 C (-27.0 F)
1975	-33.3 C (-27.9 F)
1976	-30.0 C (-22.0 F)
1977	-31.7 C (-25.1 F)
1978	-37.2 C (-35.0 F)
1979	-34.4 C (-29.9 F)
1980	-34.4 C (-29.9 F)
1981	-36.7 C (-34.1 F)
1982	-35.6 C (-32.1 F)
1983	-40.0 C (-40.0 F)
1984	-31.7 C (-25.1 F)
1985	-33.9 C (-29.0 F)
1986	-32.2 C (-26.0 F)
1987	-31.1 C (-24.0 F)
1988	-29.4 C (-20.9 F)
1989	-39.4 C (-38.9 F)
1990	-41.1 C (-42.0 F)
1991	-31.7 C (-25.1 F)
1992	-30.0 C (-22.0 F)
1993	-29.4 C (-20.9 F)
1994	-33.9 C (-29.0 F)
1995	-28.9 C (-20.0 F)
1996	-38.3 C (-36.9 F)
1997	-31.1 C (-24.0 F)
1998	-32.2 C (-26.0 F)
1999	-22.8 C (-9.0 F)
2000	-28.9 C (-20.0 F)
2001	-23.3 C (-9.9 F)
2002	-29.4 C (-20.9 F)
2003	-30.6 C (-23.1 F)
2004	-37.2 C (-35.0 F)
2005	-31.7 C (-25.1 F)
2006	-31.7 C (-25.1 F)
2007	-28.3 C (-18.9 F)
2008	-32.8 C (-27.0 F)
2009	-32.8 C (-27.0 F)
2010	-32.8 C (-27.0 F)
2011	-30.0 C (-22.0 F)
2012	-22.8 C (-9.0 F)
2013	-30.6 C (-23.1 F)
2014	-33.9 C (-29.0 F)
2015	-24.4 C (-11.9 F)
2016	-37.2 C (-35.0 F)
2017	-31.1 C (-24.0 F)
2018	-26.7 C (-16.1 F)
2019	-36.7 C (-34.1 F)
2020	-21.1 C (-6.0 F)
2021	-26.7 C (-16.1 F)
2022	-34.4 C (-29.9 F)
2023	-28.9 C (-20.0 F)
2024	-36.1 C (-33.0 F)
2025	-32.8 C (-27.0 F)
2026	-24.4 C (-11.9 F)

Wettest day (Rx1day)

The wettest day of the year at Boulder, 1880 to 2026. The record is 47.0 mm (1.9 in) in 1983, marked on the chart; the median year is 21.6 mm (0.9 in).

Wettest day (Rx1day) at Boulder by year
Year	Wettest day (Rx1day)
1880	0.0 mm (0.00 in)
1948	20.6 mm (0.8 in)
1949	21.3 mm (0.8 in)
1950	21.1 mm (0.8 in)
1951	12.4 mm (0.5 in)
1952	25.4 mm (1.0 in)
1953	16.8 mm (0.7 in)
1954	14.2 mm (0.6 in)
1955	34.8 mm (1.4 in)
1956	13.5 mm (0.5 in)
1957	17.8 mm (0.7 in)
1958	19.8 mm (0.8 in)
1959	22.1 mm (0.9 in)
1960	17.8 mm (0.7 in)
1961	18.3 mm (0.7 in)
1962	15.5 mm (0.6 in)
1963	22.1 mm (0.9 in)
1964	16.8 mm (0.7 in)
1965	13.2 mm (0.5 in)
1966	10.7 mm (0.4 in)
1967	19.1 mm (0.8 in)
1968	19.8 mm (0.8 in)
1969	27.9 mm (1.1 in)
1970	16.8 mm (0.7 in)
1971	26.7 mm (1.1 in)
1972	19.8 mm (0.8 in)
1973	15.7 mm (0.6 in)
1974	30.5 mm (1.2 in)
1975	33.0 mm (1.3 in)
1976	35.6 mm (1.4 in)
1977	15.2 mm (0.6 in)
1978	19.1 mm (0.8 in)
1979	19.8 mm (0.8 in)
1980	33.5 mm (1.3 in)
1981	43.2 mm (1.7 in)
1982	25.4 mm (1.0 in)
1983	47.0 mm (1.9 in)
1984	26.9 mm (1.1 in)
1985	20.8 mm (0.8 in)
1986	19.3 mm (0.8 in)
1987	26.2 mm (1.0 in)
1988	29.7 mm (1.2 in)
1989	21.6 mm (0.9 in)
1990	37.1 mm (1.5 in)
1991	37.1 mm (1.5 in)
1992	20.3 mm (0.8 in)
1993	23.9 mm (0.9 in)
1994	24.4 mm (1.0 in)
1995	30.0 mm (1.2 in)
1996	16.8 mm (0.7 in)
1997	26.7 mm (1.1 in)
1998	15.2 mm (0.6 in)
1999	14.7 mm (0.6 in)
2000	15.0 mm (0.6 in)
2001	25.4 mm (1.0 in)
2002	27.2 mm (1.1 in)
2003	11.9 mm (0.5 in)
2004	33.0 mm (1.3 in)
2005	42.4 mm (1.7 in)
2006	38.9 mm (1.5 in)
2007	18.5 mm (0.7 in)
2008	21.6 mm (0.9 in)
2009	33.5 mm (1.3 in)
2010	27.2 mm (1.1 in)
2011	15.5 mm (0.6 in)
2012	27.9 mm (1.1 in)
2013	25.7 mm (1.0 in)
2014	26.9 mm (1.1 in)
2015	17.0 mm (0.7 in)
2016	17.0 mm (0.7 in)
2017	24.6 mm (1.0 in)
2018	20.3 mm (0.8 in)
2019	20.3 mm (0.8 in)
2020	41.9 mm (1.6 in)
2021	29.2 mm (1.1 in)
2022	24.4 mm (1.0 in)
2023	39.4 mm (1.6 in)
2024	22.9 mm (0.9 in)
2025	33.8 mm (1.3 in)
2026	7.6 mm (0.30 in)

Wettest five days (Rx5day)

The wettest five days of the year at Boulder, 1880 to 2026. The record is 74.0 mm (2.9 in) in 2006, marked on the chart; the median year is 36.1 mm (1.4 in).

Wettest five days (Rx5day) at Boulder by year
Year	Wettest five days (Rx5day)
1880	n/a
1948	28.7 mm (1.1 in)
1949	31.3 mm (1.2 in)
1950	23.4 mm (0.9 in)
1951	25.9 mm (1.0 in)
1952	41.9 mm (1.6 in)
1953	38.1 mm (1.5 in)
1954	21.5 mm (0.8 in)
1955	39.1 mm (1.5 in)
1956	23.6 mm (0.9 in)
1957	28.2 mm (1.1 in)
1958	37.7 mm (1.5 in)
1959	29.5 mm (1.2 in)
1960	24.3 mm (1.0 in)
1961	28.5 mm (1.1 in)
1962	30.8 mm (1.2 in)
1963	40.9 mm (1.6 in)
1964	37.3 mm (1.5 in)
1965	29.0 mm (1.1 in)
1966	19.4 mm (0.8 in)
1967	38.2 mm (1.5 in)
1968	27.4 mm (1.1 in)
1969	39.8 mm (1.6 in)
1970	31.6 mm (1.2 in)
1971	36.6 mm (1.4 in)
1972	27.0 mm (1.1 in)
1973	27.4 mm (1.1 in)
1974	30.8 mm (1.2 in)
1975	49.3 mm (1.9 in)
1976	63.8 mm (2.5 in)
1977	27.0 mm (1.1 in)
1978	38.6 mm (1.5 in)
1979	22.1 mm (0.9 in)
1980	62.7 mm (2.5 in)
1981	60.2 mm (2.4 in)
1982	48.3 mm (1.9 in)
1983	68.4 mm (2.7 in)
1984	32.7 mm (1.3 in)
1985	30.4 mm (1.2 in)
1986	35.9 mm (1.4 in)
1987	37.5 mm (1.5 in)
1988	37.7 mm (1.5 in)
1989	31.5 mm (1.2 in)
1990	61.0 mm (2.4 in)
1991	51.1 mm (2.0 in)
1992	47.2 mm (1.9 in)
1993	36.1 mm (1.4 in)
1994	27.7 mm (1.1 in)
1995	58.4 mm (2.3 in)
1996	24.2 mm (1.0 in)
1997	43.4 mm (1.7 in)
1998	40.7 mm (1.6 in)
1999	31.5 mm (1.2 in)
2000	27.0 mm (1.1 in)
2001	36.9 mm (1.5 in)
2002	40.8 mm (1.6 in)
2003	25.4 mm (1.0 in)
2004	49.0 mm (1.9 in)
2005	54.4 mm (2.1 in)
2006	74.0 mm (2.9 in)
2007	43.2 mm (1.7 in)
2008	40.4 mm (1.6 in)
2009	41.2 mm (1.6 in)
2010	43.0 mm (1.7 in)
2011	24.2 mm (1.0 in)
2012	33.7 mm (1.3 in)
2013	44.7 mm (1.8 in)
2014	57.3 mm (2.3 in)
2015	29.5 mm (1.2 in)
2016	27.7 mm (1.1 in)
2017	25.9 mm (1.0 in)
2018	45.2 mm (1.8 in)
2019	16.5 mm (0.6 in)
2020	11.4 mm (0.4 in)
2021	29.2 mm (1.1 in)
2022	42.4 mm (1.7 in)
2023	39.4 mm (1.6 in)
2024	29.6 mm (1.2 in)
2025	38.9 mm (1.5 in)
2026	0.3 mm (0.01 in)

Longest dry spell (CDD)

The longest dry spell of the year at Boulder, 1880 to 2026. The record is 82 days in 1999, marked on the chart; the median year is 33 days.

Longest dry spell (CDD) at Boulder by year
Year	Longest dry spell (CDD)
1880	1 day
1948	36 days
1949	43 days
1950	27 days
1951	44 days
1952	42 days
1953	50 days
1954	33 days
1955	57 days
1956	34 days
1957	20 days
1958	29 days
1959	55 days
1960	22 days
1961	28 days
1962	22 days
1963	36 days
1964	31 days
1965	33 days
1966	29 days
1967	31 days
1968	24 days
1969	35 days
1970	31 days
1971	23 days
1972	25 days
1973	43 days
1974	31 days
1975	21 days
1976	44 days
1977	40 days
1978	27 days
1979	49 days
1980	23 days
1981	30 days
1982	27 days
1983	64 days
1984	60 days
1985	44 days
1986	25 days
1987	58 days
1988	47 days
1989	19 days
1990	40 days
1991	40 days
1992	28 days
1993	35 days
1994	37 days
1995	21 days
1996	34 days
1997	35 days
1998	65 days
1999	82 days
2000	33 days
2001	36 days
2002	56 days
2003	28 days
2004	34 days
2005	54 days
2006	56 days
2007	30 days
2008	23 days
2009	54 days
2010	53 days
2011	32 days
2012	23 days
2013	22 days
2014	24 days
2015	18 days
2016	30 days
2017	41 days
2018	10 days
2019	15 days
2020	31 days
2021	34 days
2022	26 days
2023	17 days
2024	37 days
2025	12 days
2026	5 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

64 years with a frost

Across 64 years with a frost, the median last spring frost at Boulder falls on 9 June and the median first autumn frost on 4 September, which leaves a median of 89 days between them.

In 1989 to 2024 the median growing season was 91 days. That is 2 days more than in 1949 to 1984.

Fitted over all years, the growing season changes by +1.2 days per decade at this station.

Frost dates and growing season at Boulder
Measure	Median, all years	Earliest period (1949 to 1984)	Recent period (1989 to 2024)	Recent against earliest	Fitted trend
Last spring frost	9 June	11 June	10 June	1 day earlier	-0.3 days per decade
First autumn frost	4 September	3 September	5 September	2 days later	+0.9 days per decade
Growing days	89 days	89 days	91 days	2 days more	+1.2 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

68 years, 1949 to 2024

A day with at least 22.3 mm (0.9 in) of rain is expected about once in 2 years. A day with at least 50.3 mm (2.0 in) of rain is expected about once in 100 years.

Rainfall return levels at Boulder: the daily rain expected about once in a given number of years
Expected about once in	A day with at least	Note
2 years	22.3 mm (0.9 in)
5 years	29.7 mm (1.2 in)
10 years	34.7 mm (1.4 in)
25 years	40.9 mm (1.6 in)
50 years	45.6 mm (1.8 in)
100 years	50.3 mm (2.0 in)	Longer than the 68 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, 68 years of values from 1949 to 2024.

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: 47.0 mm (1.9 in) in 1983; 43.2 mm (1.7 in) in 1981; 42.4 mm (1.7 in) in 2005.

Station Changes

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

Climate Twins

2004 to 2024 against 1961 to 1990

Over 2004 to 2024, Boulder had a mean temperature of 6.4 C (43.4 F) and 254.1 mm (10.0 in) of rain a year. The 3 stations whose 1961 to 1990 climate was closest to that are Wells (United States, 613 km away), Dillon AP (United States, 113 km away) and Burris (United States, 389 km away).

Climate twins of Boulder: stations whose 1961 to 1990 climate is closest to its 2004 to 2024 climate
Twin station	Country	Distance away	Mean temperature, 1961-1990	Rain a year, 1961-1990	Climate difference
Wells	United States	613 km (381 mi)	6.7 C (44.0 F)	270.3 mm (10.6 in)	0.60
Dillon AP	United States	113 km (70 mi)	6.0 C (42.8 F)	259.6 mm (10.2 in)	0.74
Burris	United States	389 km (242 mi)	6.3 C (43.3 F)	224.3 mm (8.8 in)	0.76

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 Boulder standing records by year: CSV or JSON. Field meanings are on the data page.
Data for Boulder 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 2026-10-15 (15 October 2026). Records are computed by this site and are not official.

Data as of 2026-10-15. Last revised 15 October 2026 (2026-10-15).