Heart Butte Dam Threshold Days by Year (USC00324091)

18 fixed thresholds counted per year at Heart Butte Dam (USC00324091): hot days, frost, tropical nights and heavy rain, with the most days in a year.

Key Facts for Heart Butte Dam Thresholds

Heart Butte Dam: days with a maximum temperature at or above 30 C (86 F) in 40 years, most in 1988 with 63.
Heart Butte Dam: days with a maximum temperature at or above 90 F (32.2 C) in 40 years, most in 1988 with 49.
Heart Butte Dam: days with a maximum temperature at or below 0 C (32 F) in 40 years, most in 1996 with 108.
Heart Butte Dam: nights with a minimum temperature at or below 0 C (32 F) in 40 years, most in 2002 with 204.
18 fixed thresholds have at least one qualifying day at Heart Butte Dam.

Days at or above 30 C (86 F)

40 years with a qualifying day

Days per year at Heart Butte Dam with a maximum temperature at or above 30 C (86 F), with the decade average as a line. The most was 63 in 1988.

Days at or above 30 C (86 F) per year at Heart Butte Dam
Year	Days	Decade average
1985	31	41.8
1986	23	41.8
1987	42	41.8
1988	63	41.8
1989	50	41.8
1990	48	33.5
1991	34	33.5
1992	22	33.5
1993	11	33.5
1994	26	33.5
1995	32	33.5
1996	36	33.5
1997	43	33.5
1998	49	33.5
1999	34	33.5
2000	43	42.2
2001	44	42.2
2002	52	42.2
2003	57	42.2
2004	27	42.2
2005	38	42.2
2006	59	42.2
2007	42	42.2
2008	42	42.2
2009	18	42.2
2010	28	29.8
2011	28	29.8
2012	44	29.8
2013	27	29.8
2014	19	29.8
2015	37	29.8
2016	32	29.8
2017	39	29.8
2018	30	29.8
2019	14	29.8
2020	32	34.4
2021	51	34.4
2022	32	34.4
2023	28	34.4
2026	29	34.4

For each year, a bar from the first to the last day at Heart Butte Dam meeting 30 C (86 F).

First to last qualifying date each year at Heart Butte Dam
Year	First date	Last date
1985	1985-05-04	1985-09-16
1986	1986-05-05	1986-08-25
1987	1987-04-19	1987-10-04
1988	1988-04-08	1988-10-01
1989	1989-04-23	1989-10-01
1990	1990-04-22	1990-09-26
1991	1991-05-22	1991-10-17
1992	1992-05-07	1992-10-02
1993	1993-05-14	1993-09-12
1994	1994-04-18	1994-09-10
1995	1995-06-14	1995-09-16
1996	1996-06-09	1996-10-06
1997	1997-06-01	1997-10-18
1998	1998-05-18	1998-09-29
1999	1999-05-29	1999-09-23
2000	2000-06-08	2000-10-19
2001	2001-04-29	2001-09-06
2002	2002-05-29	2002-09-17
2003	2003-04-13	2003-10-19
2004	2004-06-04	2004-10-05
2005	2005-06-17	2005-10-01
2006	2006-05-18	2006-09-14
2007	2007-05-18	2007-09-29
2008	2008-07-01	2008-09-20
2009	2009-06-26	2009-09-20
2010	2010-05-29	2010-09-29
2011	2011-06-03	2011-10-05
2012	2012-04-24	2012-09-30
2013	2013-05-14	2013-09-23
2014	2014-05-24	2014-09-27
2015	2015-06-09	2015-10-11
2016	2016-05-06	2016-09-12
2017	2017-05-08	2017-09-13
2018	2018-05-26	2018-09-08
2019	2019-05-16	2019-09-18
2020	2020-06-14	2020-09-23
2021	2021-06-04	2021-10-06
2022	2022-06-19	2022-09-20
2023	2023-06-02	2023-09-19
2026	2026-05-26	2026-09-11

Every Fixed Threshold

Fixed thresholds at Heart Butte Dam
Threshold	Years with a qualifying day	Most days in a year	Year	Latest year days
30 C (86 F): Days	40	63	1988	29
35 C (95 F): Days	38	26	1988	10
40 C (104 F): Days	11	5	2003	3
90 F (32.2 C): Days	40	49	1988	18
100 F (37.8 C): Days	25	11	1988	5
110 F (43.3 C): Days	3	1	2002	1
0 C (32 F): Ice days (max	40	108	1996	19
0 C (32 F): Frost days (min	40	204	2002	70
-10 C (14 F): Days with min	40	110	1996	19
-20 C (-4 F): Days with min	40	52	1996	7
-30 C (-22 F): Days with min	31	18	1996	3
20 C (68 F): Tropical nights (min	27	6	2003	2
10 mm (0.39 in): Days with 10 mm or more rain	35	21	1986	3
25 mm (0.98 in): Days with 25 mm or more rain	32	7	2000	1
50 mm (1.97 in): Days with 50 mm or more rain	11	2	1986	1
100 mm (3.94 in): Days with 100 mm or more rain	1	1	2001	1
10 cm (3.9 in): Days with 10 cm or more snowfall	19	8	2009	2
25 cm (9.8 in): Days with 25 cm or more snowfall	3	2	2009	2

Years with under 90 percent of days observed are left out of the most days column. Threshold history at this station starts in 1985.

Download the Data

Data for Heart Butte 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 2026-10-17 (17 October 2026). Threshold counts are computed by this site.

Data as of 2026-10-17. Last revised 17 October 2026 (2026-10-17).

Heart Butte Dam Threshold Days by Year (USC00324091)

Key Facts for Heart Butte Dam Thresholds

Days at or above 30 C (86 F)

Every Fixed Threshold

Download the Data

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