Frost history / Mt Hamilton, CA
Mt Hamilton, CA: frost dates by year
Last spring and first fall frost at NOAA station USC00045933, 1951 to 2025, measured from daily minimum temperatures.
Elevation 4,206 ft, 37.344, -121.642. Download the data (JSON) · NOAA daily records
Summary at 32°F
| Last spring frost | First fall frost | |
|---|---|---|
| Median | May 11 | Nov 17 |
| Earliest | Mar 13 (2019) | Oct 4 (2009) |
| Latest | Jun 12 (1952) | Dec 25 (2014) |
| Trend | 3.1 days earlier per decade | 2.4 days later per decade |
| Years with data | 65 | 62, 1 with no freeze |
At 28°F (hard freeze) the median last spring date is Apr 15 and the median first fall date is Nov 30.
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 | Apr 26 | none | Mar 14 | none |
| 2024 | May 6 | Nov 15 | Apr 6 | none |
| 2023 | May 2 | Dec 8 | Apr 19 | none |
| 2022 | May 11 | Nov 3 | Apr 13 | Dec 1 |
| 2021 | May 20 | Dec 9 | Mar 16 | Dec 14 |
| 2020 | Apr 6 | Nov 7 | Mar 26 | Nov 8 |
| 2019 | Mar 13 | Nov 26 | Mar 9 | Nov 26 |
| 2018 | Apr 19 | Dec 2 | Mar 25 | none |
| 2017 | May 13 | Nov 5 | Mar 6 | Dec 20 |
| 2016 | Apr 25 | Dec 1 | Feb 1 | Dec 16 |
| 2015 | May 12 | Nov 10 | none | Nov 25 |
| 2014 | Apr 25 | Dec 25 | Feb 5 | Dec 30 |
| 2013 | May 23 | Nov 21 | Apr 16 | Dec 4 |
| 2012 | May 25 | Nov 8 | Apr 7 | Dec 13 |
| 2011 | May 29 | no data | Apr 13 | no data |
| 2010 | May 24 | Nov 20 | May 22 | Nov 21 |
| 2009 | Apr 29 | Oct 4 | Apr 29 | Dec 6 |
| 2008 | Apr 30 | Dec 14 | Apr 30 | Dec 14 |
| 2007 | May 3 | Dec 1 | Apr 19 | Dec 1 |
| 2006 | Apr 17 | Nov 23 | Apr 17 | Nov 26 |
| 2005 | Apr 14 | Nov 26 | Apr 13 | Dec 2 |
| 2004 | Apr 18 | Nov 4 | Feb 27 | Nov 28 |
| 2003 | May 10 | Oct 30 | Apr 15 | Nov 22 |
| 2002 | May 10 | Dec 17 | Apr 28 | Dec 19 |
| 2001 | Apr 21 | Nov 24 | Apr 21 | Dec 4 |
| 2000 | May 11 | Nov 9 | Apr 28 | Nov 14 |
| 1999 | Jun 3 | Nov 21 | Apr 28 | Dec 10 |
| 1998 | May 27 | Nov 9 | Apr 15 | Dec 4 |
| 1997 | Apr 9 | Nov 30 | Apr 9 | Dec 9 |
| 1996 | Apr 21 | Oct 26 | Mar 28 | none |
| 1995 | May 13 | Dec 16 | Apr 16 | none |
| 1994 | Apr 26 | Nov 2 | Mar 23 | Nov 3 |
| 1993 | May 12 | Nov 12 | Mar 1 | Nov 23 |
| 1992 | Apr 4 | Nov 20 | none | Dec 8 |
| 1991 | May 19 | Oct 27 | May 1 | Nov 30 |
| 1990 | May 24 | Nov 20 | Mar 13 | Nov 20 |
| 1989 | Mar 26 | Nov 26 | Mar 3 | none |
| 1988 | May 17 | Nov 18 | May 5 | Dec 15 |
| 1987 | Apr 19 | Nov 25 | Apr 18 | Dec 12 |
| 1986 | May 21 | Nov 29 | May 6 | Dec 24 |
| 1985 | May 30 | no data | Apr 20 | no data |
| 1984 | Apr 26 | Oct 16 | Apr 26 | Dec 13 |
| 1983 | May 10 | Nov 18 | Apr 12 | Nov 21 |
| 1982 | Jun 3 | Nov 8 | Apr 15 | Dec 27 |
| 1981 | May 16 | Oct 28 | Mar 21 | Nov 26 |
| 1980 | Jun 5 | Nov 24 | May 23 | Dec 7 |
| 1979 | May 8 | Nov 19 | Apr 18 | none |
| 1978 | Apr 21 | Nov 10 | Apr 7 | Nov 11 |
| 1977 | May 16 | Nov 19 | Mar 30 | Nov 19 |
| 1976 | Apr 26 | Nov 27 | Apr 16 | Nov 27 |
| 1975 | May 20 | Oct 23 | May 20 | Nov 17 |
| 1974 | May 19 | no data | May 15 | no data |
| 1973 | Apr 19 | Nov 3 | Apr 1 | Nov 17 |
| 1972 | May 19 | Oct 30 | Apr 13 | Dec 4 |
| 1971 | Jun 1 | Oct 16 | Apr 24 | Oct 19 |
| 1970 | May 11 | Nov 28 | Apr 28 | Nov 28 |
| 1969 | no data | Nov 16 | no data | Dec 27 |
| 1968 | May 14 | Nov 4 | Apr 17 | Nov 14 |
| 1963 | May 9 | no data | Apr 21 | no data |
| 1962 | no data | Nov 17 | no data | Nov 29 |
| 1958 | May 12 | no data | May 12 | no data |
| 1957 | Apr 21 | Nov 2 | Mar 22 | Dec 22 |
| 1956 | May 12 | Oct 23 | Apr 13 | Dec 6 |
| 1955 | May 15 | Nov 12 | Apr 27 | Nov 12 |
| 1954 | Jun 9 | Nov 28 | Mar 30 | Nov 29 |
| 1953 | Jun 10 | no data | Jun 2 | no data |
| 1952 | Jun 12 | Nov 14 | Mar 21 | Nov 15 |
| 1951 | no data | Oct 25 | no data | Nov 23 |
"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 1991–2020 frost probabilities.