Frost history / Hebgen Dam, MT
Hebgen Dam, MT: frost dates by year
Last spring and first fall frost at NOAA station USC00244038, 1951 to 2025, measured from daily minimum temperatures.
Elevation 6,489 ft, 44.867, -111.339. Download the data (JSON), NOAA daily records
Summary at 32°F
| Last spring frost | First fall frost | |
|---|---|---|
| Median | Jun 22 | Sep 3 |
| Earliest | May 30 (2004) | Aug 1 (1975) |
| Latest | Jul 22 (1954) | Sep 29 (2023) |
| Trend | 2.8 days earlier per decade | 2.1 days later per decade |
| Years with data | 59 | 61 |
At 28°F (hard freeze) the median last spring date is May 26 and the median first fall date is Sep 19.
The trend is a straight-line fit through the years with a freeze. A positive spring trend means the last frost now comes later. Short or patchy records give noisy trends.
Chart
Last spring frost (32°F)
First fall frost (32°F)
Dots are single years. The gray line is the median, the green line the fitted trend.
Year by year
| Year | Last spring 32°F | First fall 32°F | Last spring 28°F | First fall 28°F |
|---|---|---|---|---|
| 2025 | Jun 22 | Sep 23 | May 2 | Oct 7 |
| 2024 | Jun 20 | Sep 22 | May 21 | Oct 1 |
| 2023 | Jun 22 | Sep 29 | May 10 | Oct 25 |
| 2022 | Jun 25 | Sep 10 | May 23 | Oct 14 |
| 2021 | Jun 11 | Sep 17 | May 22 | Sep 29 |
| 2020 | Jun 15 | Sep 7 | May 8 | Sep 8 |
| 2018 | Jun 12 | Sep 17 | Jun 12 | Sep 25 |
| 2016 | May 31 | no data | May 12 | no data |
| 2014 | no data | Sep 4 | no data | Sep 12 |
| 2013 | Jun 21 | no data | May 3 | no data |
| 2011 | Jun 4 | Sep 20 | Jun 4 | Oct 17 |
| 2010 | Jun 18 | Aug 31 | May 23 | Oct 12 |
| 2009 | Jun 23 | Aug 17 | May 22 | Oct 1 |
| 2008 | Jun 13 | Sep 1 | Jun 11 | Oct 8 |
| 2007 | Jun 9 | Sep 10 | May 24 | Sep 10 |
| 2006 | Jun 1 | Aug 31 | May 11 | Sep 24 |
| 2005 | no data | Aug 14 | no data | Oct 5 |
| 2004 | May 30 | Sep 4 | May 25 | Sep 22 |
| 2003 | Jun 25 | Sep 9 | May 20 | Sep 13 |
| 2002 | Jul 13 | Aug 8 | Jun 20 | Sep 21 |
| 2001 | no data | Sep 8 | no data | Oct 5 |
| 1999 | Jul 16 | Sep 7 | Jun 9 | Sep 27 |
| 1997 | no data | Sep 18 | no data | Sep 21 |
| 1996 | Jun 19 | no data | May 10 | no data |
| 1995 | Jun 20 | Sep 21 | Jun 7 | Sep 21 |
| 1994 | Jun 17 | Sep 4 | Apr 30 | Sep 22 |
| 1993 | no data | Aug 30 | no data | Sep 14 |
| 1992 | Jul 14 | Aug 23 | Jul 14 | Aug 25 |
| 1991 | Jun 15 | Sep 16 | Jun 15 | Sep 18 |
| 1990 | Jun 13 | Sep 21 | May 16 | Oct 3 |
| 1989 | Jun 22 | Sep 10 | May 26 | Sep 11 |
| 1988 | Jun 30 | Aug 28 | May 20 | Sep 12 |
| 1987 | Jun 3 | Aug 17 | Jun 3 | Sep 17 |
| 1986 | no data | Sep 21 | no data | Sep 22 |
| 1985 | Jun 27 | Aug 14 | May 15 | Sep 20 |
| 1984 | Jun 2 | Sep 8 | Jun 2 | Sep 14 |
| 1983 | Jun 14 | Sep 6 | May 31 | Sep 19 |
| 1982 | Jun 9 | Sep 12 | Jun 9 | Sep 14 |
| 1981 | Jul 8 | Aug 31 | May 12 | Sep 23 |
| 1980 | Jun 13 | Aug 4 | May 13 | Sep 22 |
| 1979 | Jun 19 | Sep 11 | Jun 9 | Sep 12 |
| 1978 | Jun 20 | Aug 19 | May 31 | Sep 14 |
| 1977 | Jul 7 | Aug 28 | May 29 | Sep 9 |
| 1976 | Jun 26 | Aug 27 | Jun 26 | Sep 8 |
| 1975 | Jun 28 | Aug 1 | Jun 10 | Sep 19 |
| 1974 | Jun 9 | Aug 10 | Jun 1 | Sep 2 |
| 1973 | Jul 2 | Sep 3 | Jun 19 | Sep 15 |
| 1972 | Jul 4 | Sep 8 | May 13 | Sep 20 |
| 1971 | Jun 30 | Aug 24 | May 19 | Sep 15 |
| 1970 | Jun 13 | Sep 9 | Jun 1 | Sep 10 |
| 1969 | Jul 4 | Aug 31 | Jun 14 | Sep 16 |
| 1968 | Jun 29 | Aug 29 | Jun 14 | Oct 3 |
| 1967 | Jun 24 | Sep 13 | May 20 | Sep 13 |
| 1966 | Jun 26 | Aug 21 | Jun 25 | Sep 30 |
| 1965 | Jun 28 | Aug 29 | May 27 | Aug 30 |
| 1960 | Jun 22 | no data | Jun 21 | no data |
| 1959 | Jul 8 | Aug 14 | Jun 1 | Sep 2 |
| 1958 | Jul 15 | Aug 30 | May 10 | Sep 20 |
| 1957 | Jul 4 | Sep 9 | May 22 | Sep 14 |
| 1956 | Jun 22 | Aug 31 | May 15 | Aug 31 |
| 1955 | Jul 8 | Sep 16 | Jul 2 | Sep 22 |
| 1954 | Jul 22 | Aug 27 | Jun 18 | Sep 18 |
| 1953 | Jun 27 | Sep 3 | May 25 | Oct 3 |
| 1952 | Jul 7 | Sep 1 | May 18 | Sep 14 |
| 1951 | Jul 12 | Aug 31 | Jun 3 | Sep 12 |
"none" means the station recorded no freeze at that threshold in that half of the year. "no data" means more than 10% of the season's daily readings were missing. Years with no usable data are left out. See the methodology for the rules, and the ZIP lookup for 1991 to 2020 frost probabilities.