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 21403
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 21403 in zone 8a (the coldest night of a typical year: 10 to 15°F).
The nearest station, Annapolis, MD, is 3 miles from the ZIP's center: its last spring frost comes after March 23 in half of years and after April 6 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 |
|---|---|---|---|---|---|---|
| Annapolis, MDAnnapolis Naf | 3 mi | 8 ft | March 23 | April 6 | November 20 | 8a |
| Annapolis Police Barracks, MD | 4 mi | 25 ft | March 27 | April 9 | November 13 | – |
| Stevensville, MD2 mi SW | 8 mi | 10 ft | March 29 | April 8 | November 12 | – |
| Upper Marlboro, MD3 mi NNW | 16 mi | 130 ft | April 9 | April 24 | October 29 | 7b |
| Glenn Dale, MDGlenn Dale Bell Station | 17 mi | 150 ft | April 22 | May 9 | October 22 | – |
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 Annapolis
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 11 | April 5 | March 22 | November 6 | October 25 |
| 32°F | April 6 | March 31 | March 23 | March 8 | November 20 | November 4 |
| 28°F (hard freeze) | March 28 | March 18 | March 12 | February 24 | December 3 | November 16 |
| 24°F | March 19 | March 8 | March 1 | February 9 | December 18 | November 30 |
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.