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 20877
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 20877 in zone 7b (the coldest night of a typical year: 5 to 10°F).
The nearest station, Rockville, MD, is 4 miles from the ZIP's center: its last spring frost comes after April 1 in half of years and after April 15 in one year in ten. By the USDA's method its plant hardiness zone is 7b.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Rockville, MD1 mi NE | 4 mi | 440 ft | April 1 | April 15 | November 6 | 7b |
| Damascus, MD3 mi SSW | 9 mi | 700 ft | April 14 | May 2 | October 29 | 7a |
| Dalecarlia Reservoir, MD | 15 mi | 150 ft | April 9 | April 26 | October 31 | 7b |
| Beltsville, MD | 16 mi | 145 ft | April 10 | May 1 | November 1 | 7b |
| Laurel, MD3 mi W | 16 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 Rockville
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 5 | April 23 | April 16 | March 31 | October 25 | October 12 |
| 32°F | April 15 | April 6 | April 1 | March 19 | November 6 | October 24 |
| 28°F (hard freeze) | April 4 | March 28 | March 22 | March 5 | November 19 | November 5 |
| 24°F | March 25 | March 16 | March 10 | February 23 | December 2 | November 14 |
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.