Frost dates by state and ZIP code: Last spring and first autumn frost, NOAA 1991-2020
NOAA publishes, for every station with a long enough record, the dates after which the last spring frost and before which the first autumn frost come in one year in ten, half of years and nine in ten. PlainClimate shows all three at 32°F and at the hard-freeze 28°F, for every station and for the nearest stations to any ZIP code.
How do I read a frost date?
Take Chicago O'Hare: the last spring frost comes after April 16 in half of years, after May 1 in one year in ten, and after April 3 in nine years in ten. Planting tender plants on the median date leaves an even chance of one more frost; waiting for the 1-in-10 date cuts it to about one year in ten.
A frost here means a night at 32°F or colder at the station's thermometer, about five feet above the ground. Low spots and open ground can frost on nights the station stays above 32°F, so gardeners often add a margin.
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities).
When is the last frost in each state?
| State | Places | Earliest | Latest |
|---|---|---|---|
| Alaska | 132 | April 4 | June 12 |
| Alabama | 92 | January 31 | April 11 |
| Arkansas | 102 | March 10 | April 15 |
| Arizona | 164 | January 4 | June 21 |
| California | 293 | January 1 | December 31 |
| Colorado | 176 | April 17 | June 21 |
| Connecticut | 20 | April 5 | May 11 |
| District of Columbia | 1 | March 24 | March 24 |
| Delaware | 7 | March 29 | April 11 |
| Florida | 120 | January 15 | March 21 |
| Georgia | 113 | February 9 | April 26 |
| Hawaii | 2 | January 26 | April 12 |
| Iowa | 134 | April 10 | May 8 |
| Idaho | 115 | April 2 | June 19 |
| Illinois | 156 | April 2 | May 2 |
| Indiana | 106 | April 2 | May 1 |
| Kansas | 153 | April 4 | May 9 |
| Kentucky | 91 | March 27 | May 1 |
| Louisiana | 81 | January 23 | March 30 |
| Massachusetts | 60 | April 4 | May 17 |
| Maryland | 40 | March 22 | May 9 |
| Maine | 76 | April 21 | June 2 |
| Michigan | 180 | April 17 | June 7 |
| Minnesota | 164 | April 15 | June 5 |
| Missouri | 154 | March 24 | April 27 |
| Mississippi | 85 | February 12 | April 9 |
| Montana | 189 | April 30 | June 18 |
| North Carolina | 166 | March 1 | May 16 |
| North Dakota | 112 | May 2 | May 24 |
| Nebraska | 157 | April 15 | May 30 |
| New Hampshire | 50 | April 21 | May 31 |
| New Jersey | 43 | March 26 | May 1 |
| New Mexico | 155 | March 9 | June 19 |
| Nevada | 100 | January 5 | June 16 |
| New York | 165 | March 30 | June 2 |
| Ohio | 112 | April 10 | May 10 |
| Oklahoma | 150 | March 15 | April 26 |
| Oregon | 154 | January 31 | June 11 |
| Pennsylvania | 151 | March 30 | May 24 |
| Rhode Island | 8 | April 11 | May 1 |
| South Carolina | 91 | February 4 | April 26 |
| South Dakota | 140 | April 27 | June 1 |
| Tennessee | 137 | March 16 | May 22 |
| Texas | 411 | January 6 | April 27 |
| Utah | 154 | March 9 | June 21 |
| Virginia | 114 | March 17 | May 12 |
| Vermont | 40 | April 28 | May 30 |
| Washington | 140 | February 26 | June 6 |
| Wisconsin | 183 | April 19 | June 3 |
| West Virginia | 90 | April 7 | May 15 |
| Wyoming | 102 | April 28 | June 20 |
Source: NOAA NCEI 1991-2020 annual normals.