Frost Dates for 20772 — Upper Marlboro, Maryland

Half of springs at Upper Marlboro 3 NNW, MD see their last 32°F night by April 9; only one in ten is past it by March 27, and one in ten still has one after April 24. Planting tender crops after April 15 leaves a 30% risk of a frost on them, after April 19 20%, and after April 24 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 52% of the 50 Maryland stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 29 in half of years, as early as October 14 one year in ten, and holds off past November 11 one year in ten. A hard freeze of 28°F follows 12 days later, around November 10; in spring the one-in-ten date for 28°F is April 12, 12 days before the 32°F one. The freeze-free season lasts 203 days in a typical year, longer than at 52% of the 50 Maryland stations; it reaches 222 days one year in ten and falls short of 182 one year in ten. On average 103 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 15 days longer, to about April 24, and return around October 19. Severe cold of 16°F or below comes every winter, usually between December 26 and February 25.

July is the warmest month at Upper Marlboro 3 NNW, MD, averaging 88°F by day and 67°F at night; January is the coldest at 44°F and 25°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 79% of years.

Warmth for growing adds up to 3,960 growing degree days a year (base 50°F), more than at 58% of the 50 Maryland stations. 35% of them (1,398) have built up by the end of June, and July adds the most, 857. Precipitation totals 45.1 inches a year, most in September (4.5") and least in February (2.7"); May to September bring 47% of it.

The nearest other station, Oxon Hill, MD, 12 miles west of Upper Marlboro, has a last frost 6 days earlier (April 3), a first frost 10 days later (November 8), a season 14 days longer.

The first measurable snow (0.1 inch or more) in Upper Marlboro usually arrives around December 20, and the last of the season around February 18. Those are the middle dates across the winters of 1991–2020 at Upper Marlboro 3 NNW, MD, 4.2 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 50 days after the last snow.

ZIP 20772 is 4 miles from Upper Marlboro 3 NNW, MD, which stands at 130 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 10 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 20772 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.