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 06389
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 06389 in zone 6b (the coldest night of a typical year: -5 to 0°F).
The nearest station, Norwich, CT, is 4 miles from the ZIP's center: its last spring frost comes after April 14 in half of years and after April 30 in one year in ten. By the USDA's method its plant hardiness zone is 7a.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Norwich, CTNorwich Public Utility Plant | 4 mi | 20 ft | April 14 | April 30 | October 24 | 7a |
| Willimantic, CTWillimantic Windham Airport | 13 mi | 247 ft | April 28 | May 11 | October 13 | 6b |
| Hampton, CT | 15 mi | 490 ft | April 30 | May 11 | October 15 | – |
| Groton station, CT | 15 mi | 40 ft | April 8 | April 22 | November 2 | 7a |
| Groton, CTGroton New London Airport | 17 mi | 10 ft | April 16 | April 30 | October 28 | 7a |
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 Norwich
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) | May 13 | May 5 | April 30 | April 16 | October 12 | October 1 |
| 32°F | April 30 | April 21 | April 14 | April 1 | October 24 | October 9 |
| 28°F (hard freeze) | April 16 | April 6 | April 1 | March 18 | November 5 | October 19 |
| 24°F | April 3 | March 29 | March 23 | March 6 | November 18 | November 1 |
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.