Frost Dates for 20785 — Landover, Maryland

Half of springs at Natl Arboretum Dc, MD see their last 32°F night by March 29; only one in ten is past it by March 15, and one in ten still has one after April 11. Planting tender crops after April 3 leaves a 30% risk of a frost on them, after April 6 20%, and after April 11 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 80% of the 50 Maryland stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 8 in half of years, as early as October 26 one year in ten, and holds off past November 23 one year in ten. A hard freeze of 28°F follows 12 days later, around November 20; in spring the one-in-ten date for 28°F is March 31, 11 days before the 32°F one. The freeze-free season lasts 224 days in a typical year, longer than at 84% of the 50 Maryland stations; it reaches 243 days one year in ten and falls short of 205 one year in ten. On average 84 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 12 days longer, to about April 10, and return around October 29. Severe cold of 16°F or below comes in 91% of winters, usually between January 10 and February 6.

July is the warmest month at Natl Arboretum Dc, MD, averaging 90°F by day and 71°F at night; January is the coldest at 45°F and 28°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 38% of years.

Warmth for growing adds up to 4,518 growing degree days a year (base 50°F), more than at 92% of the 50 Maryland stations. 36% of them (1,629) have built up by the end of June, and July adds the most, 941. Precipitation totals 45.6 inches a year, most in June (4.6") and least in February (2.8"); May to September bring 47% of it.

The nearest other station, Glenn Dale Bell Stn, MD, 6 miles northeast of Landover, has a last frost 24 days later (April 22), a first frost 17 days earlier (October 22), a season 41 days shorter.

The first measurable snow (0.1 inch or more) in Landover usually arrives around December 30, and the last of the season around February 23. Those are the middle dates across the winters of 1991–2020 at Natl Arboretum Dc, MD, 4.4 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 34 days after the last snow.

ZIP 20785 is 4 miles from Natl Arboretum Dc, MD, which stands at 50 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 21 other ZIP codes share the station; its figures are presented in full for 20002 (Washington). The 2023 USDA Plant Hardiness Zone Map lists ZIP 20785 in zone 7b, the band where the coldest night of the year averaged 5 to 10°F (-15.0 to -12.2°C) over 1991–2020; a zone describes winter lows, not frost dates.