Frost history / Rathbun Dam, IA
Rathbun Dam, IA: frost dates by year
Last spring and first fall frost at NOAA station USC00136910, 1970 to 2025, measured from daily minimum temperatures.
Elevation 965 ft, 40.825, -92.892. Download the data (JSON), NOAA daily records
Summary at 32°F
| Last spring frost | First fall frost | |
|---|---|---|
| Median | Apr 18 | Oct 10 |
| Earliest | Mar 25 (1998) | Sep 22 (1974) |
| Latest | May 9 (1980) | Nov 5 (1998) |
| Trend | 2.9 days earlier per decade | 4.9 days later per decade |
| Years with data | 30 | 28 |
At 28°F (hard freeze) the median last spring date is Apr 9 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 |
|---|---|---|---|---|
| 2025 | Apr 9 | Nov 3 | Apr 9 | Nov 3 |
| 2003 | Apr 11 | no data | Apr 10 | no data |
| 2002 | Apr 7 | Oct 14 | Apr 5 | Oct 20 |
| 2001 | no data | Oct 17 | no data | Oct 17 |
| 1999 | Apr 17 | no data | Mar 26 | no data |
| 1998 | Mar 25 | Nov 5 | Mar 25 | Nov 6 |
| 1997 | Apr 19 | no data | Apr 15 | no data |
| 1996 | Apr 23 | no data | Apr 9 | no data |
| 1995 | Apr 6 | Oct 22 | Apr 6 | Nov 3 |
| 1994 | Apr 8 | Oct 25 | Apr 8 | Oct 26 |
| 1993 | Apr 22 | Oct 10 | Apr 5 | Oct 30 |
| 1992 | Apr 24 | Oct 17 | Apr 13 | Oct 17 |
| 1991 | Mar 31 | Oct 6 | Mar 31 | Oct 7 |
| 1990 | Apr 18 | Oct 19 | Apr 13 | Oct 22 |
| 1989 | May 7 | Sep 24 | May 7 | Oct 20 |
| 1988 | Apr 24 | Oct 6 | Apr 24 | Oct 6 |
| 1987 | Apr 4 | Oct 3 | Apr 4 | Oct 3 |
| 1986 | Apr 22 | Oct 14 | Mar 27 | Nov 9 |
| 1985 | Apr 10 | Oct 1 | Apr 10 | Oct 1 |
| 1984 | Apr 1 | Sep 29 | Apr 1 | Oct 24 |
| 1983 | Apr 20 | no data | Apr 20 | no data |
| 1982 | Apr 21 | Oct 21 | Apr 21 | Oct 22 |
| 1981 | Apr 6 | Oct 19 | Apr 6 | Oct 23 |
| 1980 | May 9 | Oct 4 | Apr 12 | Oct 4 |
| 1979 | Apr 15 | Oct 5 | Apr 10 | Oct 5 |
| 1978 | Mar 28 | Oct 8 | Mar 27 | Oct 8 |
| 1977 | Apr 7 | Oct 13 | Apr 7 | Nov 10 |
| 1976 | May 3 | Oct 8 | Apr 12 | Oct 8 |
| 1975 | Apr 20 | Sep 26 | Apr 12 | Oct 19 |
| 1974 | Apr 24 | Sep 22 | Apr 9 | Oct 2 |
| 1972 | no data | Sep 30 | no data | Oct 19 |
| 1971 | Apr 29 | Oct 31 | Apr 10 | Nov 6 |
| 1970 | no data | Oct 10 | no data | Oct 16 |
"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.