Frost Dates for 20662 — Nanjemoy, Maryland

Half of springs at Quantico Mcas, VA see their last 32°F night by March 28; only one in ten is past it by March 14, and one in ten still has one after April 8. Planting tender crops after April 2 leaves a 30% risk of a frost on them, after April 5 20%, and after April 8 10%. The 11 days between the even-odds date and the one-in-ten date is narrower than at 94% 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 28 one year in ten, and holds off past November 25 one year in ten. A hard freeze of 28°F follows 14 days later, around November 22; in spring the one-in-ten date for 28°F is March 30, 9 days before the 32°F one. The freeze-free season lasts 226 days in a typical year, longer than at 88% of the 50 Maryland stations; it reaches 248 days one year in ten and falls short of 208 one year in ten. On average 76 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 11 days longer, to about April 8, and return around October 29. Severe cold of 16°F or below comes in 91% of winters, usually between January 8 and February 6.

July is the warmest month at Quantico Mcas, VA, averaging 88°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 36% of years.

Warmth for growing adds up to 4,379 growing degree days a year (base 50°F), more than at 86% of the 50 Maryland stations. 36% of them (1,593) have built up by the end of June, and July adds the most, 910. Precipitation totals 40.9 inches a year, most in July (4.6") and least in February (2.4"); May to September bring 47% of it.

The nearest other station, Fredericksburg Sewage, VA, 17 miles southwest of Nanjemoy, has a last frost 9 days later (April 6), a first frost 7 days earlier (November 1), a season 19 days shorter.

The first measurable snow (0.1 inch or more) in Nanjemoy usually arrives around December 31, and the last of the season around February 15. Those are the middle dates across the winters of 1991–2020 at Corbin, VA, 18 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 41 days after the last snow.

ZIP 20662 is 8 miles from Quantico Mcas, VA, which stands at 10 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 9 other ZIP codes share the station; its figures are presented in full for 22191 (Woodbridge). The 2023 USDA Plant Hardiness Zone Map lists ZIP 20662 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.