From NOAA 1991–2020 normals
How the Frost Season Moved Between the 1981–2010 and 1991–2020 Normals
State by state, the change in the last spring frost, first fall frost and freeze-free season at stations in both sets of NOAA normals.
NOAA replaces its climate normals every ten years. 3,497 of the stations behind this site's indexed pages have a yearly freeze in both the 1981–2010 and the 1991–2020 set. At the median one, the freeze-free season is 5 days longer in the newer normals; the last spring frost moved 2 days earlier and the first fall frost 3 days later. The season grew at 2,696 stations and shrank at 642.
The largest median gains are in Idaho (+8 days), New Hampshire (+8 days), Rhode Island (+8 days); the smallest in Wyoming (+1), Utah (+2), Texas (+2). The two periods share 1991–2010, so the change compares 2011–2020 with 1981–1990. Station moves and instrument changes can shift a station's normals as well.
| State | Stations | Last frost, days | First frost, days | Season, days |
|---|---|---|---|---|
| Idaho | 42 | -4 | +5 | +8 |
| New Hampshire | 29 | -4 | +3 | +8 |
| Rhode Island | 5 | -4 | +4 | +8 |
| Connecticut | 17 | -2 | +3 | +7 |
| Massachusetts | 50 | -3 | +4 | +7 |
| North Carolina | 114 | -3 | +3 | +7 |
| New Jersey | 34 | -2 | +5 | +7 |
| Nevada | 21 | -4 | +3 | +7 |
| Virginia | 91 | -3 | +4 | +7 |
| Delaware | 6 | -2 | +3 | +6 |
| Florida | 39 | -3 | +3 | +6 |
| Maryland | 28 | -2 | +3 | +6 |
| Michigan | 97 | -1 | +5 | +6 |
| Missouri | 128 | -2 | +4 | +6 |
| Mississippi | 77 | -4 | +1 | +6 |
| New York | 112 | -2 | +3 | +6 |
| Oregon | 68 | -4 | +3 | +6 |
| Pennsylvania | 114 | -1 | +4 | +6 |
| South Carolina | 70 | -3 | +1 | +6 |
| Vermont | 25 | -2 | +2 | +6 |
| Wisconsin | 126 | -1 | +4 | +6 |
| West Virginia | 67 | -2 | +4 | +6 |
| Alaska | 22 | -2 | +4 | +5 |
| Alabama | 71 | -4 | +1 | +5 |
| Arkansas | 82 | -3 | +2 | +5 |
| Illinois | 121 | -1 | +4 | +5 |
| Indiana | 94 | -1 | +4 | +5 |
| Kentucky | 56 | -2 | +3 | +5 |
| Minnesota | 105 | 0 | +3 | +5 |
| Ohio | 108 | -1 | +5 | +5 |
| Tennessee | 103 | -3 | +2 | +5 |
| Georgia | 87 | -3 | 0 | +4 |
| Iowa | 120 | +1 | +4 | +4 |
| Louisiana | 67 | -3 | -1 | +4 |
| Maine | 37 | -2 | +2 | +4 |
| North Dakota | 25 | 0 | +2 | +4 |
| Nebraska | 56 | 0 | +4 | +4 |
| South Dakota | 43 | +1 | +3 | +4 |
| Arizona | 56 | -3 | +1 | +3 |
| California | 127 | -4 | +1 | +3 |
| New Mexico | 51 | -2 | +1 | +3 |
| Washington | 96 | -2 | +2 | +3 |
| Colorado | 78 | 0 | +2 | +2 |
| Kansas | 91 | 0 | +3 | +2 |
| Montana | 50 | -1 | +2 | +2 |
| Oklahoma | 72 | -1 | +1 | +2 |
| Texas | 251 | -2 | -1 | +2 |
| Utah | 45 | -3 | 0 | +2 |
| Wyoming | 22 | 0 | +1 | +1 |
50% dates and season length at 32°F. Negative last-frost days mean an earlier spring frost; positive first-frost days a later fall frost. NOAA NCEI 1981–2010 and 1991–2020 annual normals, same station ID in both.
Computed by ArtUp Labs from NOAA NCEI U.S. Climate Normals for the stations behind this site's indexed ZIP pages, one row per station. Methodology · All guides