Frost dates by ZIP code: The nearest NOAA stations to your ZIP, 1991-2020 normals
Enter a five-digit ZIP code. PlainClimate finds its center (Census Bureau 2024) and the five nearest NOAA stations with frost dates, and shows each station's last spring and first autumn 32°F dates with its distance and elevation.
Frost dates near ZIP 37421
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 37421 in zone 8a (the coldest night of a typical year: 10 to 15°F).
The nearest station, Chattanooga, TN, is 3 miles from the ZIP's center: its last spring frost comes after March 24 in half of years and after April 8 in one year in ten. By the USDA's method its plant hardiness zone is 8a.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Chattanooga, TNChattanooga Airport | 3 mi | 671 ft | March 24 | April 8 | November 9 | 8a |
| Fort Oglethorpe, GAChickamauga Park Larc | 10 mi | 782 ft | April 6 | April 23 | October 30 | – |
| Lookout Mountain, TNLookout Mountain-Point Park | 11 mi | 2,110 ft | March 31 | April 18 | November 6 | – |
| Chickamauga, GA2 mi SW | 15 mi | 799 ft | March 25 | April 11 | November 9 | 8a |
| Soddy-Daisy, TNSoddy Daisy-Mowbray Mountain | 18 mi | 1,700 ft | April 7 | April 28 | October 29 | – |
Frost comes later in spring at higher and colder stations and earlier in low, open ground: prefer a station at a similar elevation to yours. Hardiness zone in the table: the USDA's rule (the average of each year's coldest night, 1991-2020) applied to the station's own record.
Every frost threshold at Chattanooga
NOAA publishes the dates for several temperatures and odds. A 30% spring date means a 3-in-10 chance of a later frost (the convention almanacs use); 50% is the median; 10% the cautious date.
| Threshold | Spring, 10% | Spring, 30% | Spring, 50% | Spring, 90% | Autumn, 50% | Autumn, 10% |
|---|---|---|---|---|---|---|
| 36°F (light frost) | April 20 | April 10 | April 4 | March 19 | October 31 | October 19 |
| 32°F | April 8 | March 31 | March 24 | March 6 | November 9 | October 27 |
| 28°F (hard freeze) | March 30 | March 18 | March 11 | February 18 | November 22 | November 6 |
| 24°F | March 18 | March 5 | February 23 | January 26 | December 8 | November 16 |
Source: NOAA NCEI 1991-2020 annual normals; ZIP centers: Census Bureau 2024 Gazetteer; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. Autumn 10%: one year in ten has its first frost before this date.