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 20816
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 20816 in zone 7b (the coldest night of a typical year: 5 to 10°F).
The nearest station, Dalecarlia Reservoir, MD, is 1 miles from the ZIP's center: its last spring frost comes after April 9 in half of years and after April 26 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 |
|---|---|---|---|---|---|---|
| Dalecarlia Reservoir, MD | 1 mi | 150 ft | April 9 | April 26 | October 31 | 7b |
| National Arboretum DC, MD | 9 mi | 50 ft | March 29 | April 11 | November 8 | 8a |
| Washington, DCWashington Reagan Airport | 9 mi | 10 ft | March 24 | April 6 | November 18 | 8a |
| Rockville, MD1 mi NE | 10 mi | 440 ft | April 1 | April 15 | November 6 | 7b |
| Vienna, VA | 10 mi | 418 ft | April 14 | April 28 | October 29 | 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 Dalecarlia Reservoir
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 10 | April 30 | April 23 | April 8 | October 20 | October 7 |
| 32°F | April 26 | April 16 | April 9 | March 27 | October 31 | October 16 |
| 28°F (hard freeze) | April 12 | April 3 | March 30 | March 12 | November 9 | October 29 |
| 24°F | April 2 | March 25 | March 18 | February 27 | November 22 | November 5 |
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.