Frost history / Arrowrock Dam, ID
Arrowrock Dam, ID: frost dates by year
Last spring and first fall frost at NOAA station USC00100448, 1951 to 2008, measured from daily minimum temperatures.
Elevation 3,235 ft, 43.594, -115.924. Download the data (JSON), NOAA daily records
Summary at 32°F
| Last spring frost | First fall frost | |
|---|---|---|
| Median | May 4 | Oct 8 |
| Earliest | Apr 9 (1994) | Sep 13 (1992) |
| Latest | May 30 (1977) | Oct 30 (1979) |
| Trend | little change (less than half a day per decade) | little change (less than half a day per decade) |
| Years with data | 44 | 43 |
At 28°F (hard freeze) the median last spring date is Apr 14 and the median first fall date is Oct 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 |
|---|---|---|---|---|
| 2008 | May 5 | no data | Apr 22 | no data |
| 2005 | Apr 22 | no data | Apr 14 | no data |
| 2003 | no data | Oct 10 | no data | Oct 29 |
| 2001 | no data | Oct 10 | no data | Oct 11 |
| 1999 | no data | Sep 29 | no data | Oct 18 |
| 1997 | no data | Oct 8 | no data | Oct 25 |
| 1995 | Apr 22 | no data | Apr 16 | no data |
| 1994 | Apr 9 | Oct 15 | Mar 26 | Oct 29 |
| 1993 | no data | Oct 28 | no data | Nov 5 |
| 1992 | Apr 26 | Sep 13 | Apr 8 | Oct 15 |
| 1991 | May 4 | Oct 5 | Apr 27 | Oct 28 |
| 1990 | May 16 | Oct 7 | Mar 24 | Oct 17 |
| 1989 | May 20 | Oct 16 | Mar 21 | Oct 16 |
| 1986 | May 15 | no data | Feb 14 | no data |
| 1985 | May 13 | no data | Apr 20 | no data |
| 1984 | May 8 | Sep 24 | Mar 8 | Sep 25 |
| 1983 | May 9 | Sep 21 | Apr 11 | Nov 8 |
| 1982 | May 6 | Oct 18 | Apr 21 | Oct 19 |
| 1981 | May 8 | Oct 5 | Apr 8 | Oct 5 |
| 1980 | Apr 11 | Oct 22 | Mar 26 | Oct 23 |
| 1979 | Apr 22 | Oct 30 | Apr 13 | Nov 9 |
| 1978 | Apr 23 | Oct 23 | Apr 12 | Oct 30 |
| 1977 | May 30 | Sep 22 | May 8 | Oct 11 |
| 1976 | Apr 23 | no data | Apr 19 | no data |
| 1975 | May 27 | Oct 23 | May 25 | Oct 23 |
| 1974 | May 17 | Oct 5 | Apr 12 | Oct 6 |
| 1973 | Apr 20 | Oct 4 | Apr 19 | Oct 27 |
| 1972 | May 2 | Sep 24 | May 1 | Sep 25 |
| 1971 | Apr 19 | Sep 28 | Apr 6 | Oct 16 |
| 1970 | May 14 | Sep 14 | Apr 22 | Oct 15 |
| 1969 | May 3 | Oct 3 | Mar 26 | Oct 5 |
| 1968 | May 7 | Oct 8 | May 7 | Oct 8 |
| 1967 | May 13 | Oct 15 | Apr 16 | Oct 23 |
| 1966 | May 23 | Oct 14 | Apr 27 | Oct 14 |
| 1965 | May 6 | Sep 17 | Mar 28 | Sep 18 |
| 1964 | May 6 | Oct 17 | Apr 18 | Oct 17 |
| 1963 | Apr 21 | Oct 24 | Apr 21 | Oct 26 |
| 1962 | Apr 30 | Oct 16 | Mar 30 | Nov 17 |
| 1961 | Apr 26 | Sep 22 | Apr 20 | Oct 8 |
| 1960 | May 22 | Oct 9 | Apr 23 | Oct 13 |
| 1959 | May 4 | Oct 1 | Apr 10 | Nov 5 |
| 1958 | Apr 28 | Sep 24 | Mar 31 | Nov 11 |
| 1957 | Apr 26 | Oct 6 | Mar 27 | Oct 19 |
| 1956 | May 12 | Oct 14 | Apr 8 | Oct 28 |
| 1955 | Apr 28 | Sep 29 | Apr 27 | Oct 6 |
| 1954 | May 2 | Sep 29 | Apr 10 | Sep 29 |
| 1953 | May 10 | Oct 20 | May 2 | Oct 21 |
| 1952 | Apr 12 | Oct 15 | Apr 9 | Nov 1 |
| 1951 | Apr 22 | Oct 16 | Apr 21 | Oct 30 |
"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.