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 21231
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 21231 in zone 8a (the coldest night of a typical year: 10 to 15°F).
The nearest station, Maryland Science Center Baltimore, MD, is 1 miles from the ZIP's center: its last spring frost comes after March 24 in half of years and after April 4 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 |
|---|---|---|---|---|---|---|
| Maryland Science Center Baltimore, MD | 1 mi | 20 ft | March 24 | April 4 | November 21 | 8a |
| Cylburn, MD | 6 mi | 235 ft | April 2 | April 13 | November 7 | – |
| Baltimore, MDBaltimore Wash International Airport | 10 mi | 156 ft | April 10 | April 25 | October 31 | 7b |
| Annapolis Police Barracks, MD | 21 mi | 25 ft | March 27 | April 9 | November 13 | – |
| Laurel, MD3 mi W | 22 mi | 400 ft | April 5 | April 19 | November 9 | 7b |
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 Maryland Science Center Baltimore
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 15 | April 8 | April 3 | March 22 | November 10 | October 29 |
| 32°F | April 4 | March 29 | March 24 | March 8 | November 21 | November 7 |
| 28°F (hard freeze) | March 26 | March 17 | March 11 | February 24 | December 5 | November 18 |
| 24°F | March 16 | March 8 | March 2 | February 9 | December 23 | December 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.