Frost Dates for 20678 — Prince Frederick, Maryland

Half of springs at Mechanicsville 5 NE, MD see their last 32°F night by April 17; only one in ten is past it by March 31, and one in ten still has one after May 2. Planting tender crops after April 22 leaves a 30% risk of a frost on them, after April 27 20%, and after May 2 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 27 in half of years, as early as October 12 one year in ten, and holds off past November 9 one year in ten. A hard freeze of 28°F follows 10 days later, around November 6; in spring the one-in-ten date for 28°F is April 17, 15 days before the 32°F one. The freeze-free season lasts 195 days in a typical year, shorter than at 68% of the 50 Maryland stations; it reaches 215 days one year in ten and falls short of 173 one year in ten. On average 98 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 13 days longer, to about April 30, and return around October 16. Severe cold of 16°F or below comes in 99% of winters, usually between December 20 and February 26.

July is the warmest month at Mechanicsville 5 NE, MD, averaging 85°F by day and 66°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 June to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 88% of years and May still brings one in 12% of years.

Warmth for growing adds up to 3,649 growing degree days a year (base 50°F), fewer than at 66% of the 50 Maryland stations. 36% of them (1,308) have built up by the end of June, and July adds the most, 793. Precipitation totals 48.1 inches a year, most in September (4.9") and least in February (3.0"); May to September bring 47% of it.

The nearest other station, Solomons, MD, 17 miles southeast of Prince Frederick, has a last frost 26 days earlier (March 22), a first frost 30 days later (November 26), a season 53 days longer.

The first measurable snow (0.1 inch or more) in Prince Frederick usually arrives around December 25, and the last of the season around March 6. Those are the middle dates across the winters of 1991–2020 at Mechanicsville 5 NE, MD, 8.2 miles away: half of years saw snow earlier, half later. Snow fell in 92% of those winters. The last 32°F night of spring typically comes 42 days after the last snow.

ZIP 20678 is 8 miles from Mechanicsville 5 NE, MD, which stands at 100 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 11 other ZIP codes share the station; its figures are presented in full for 20602 (Waldorf). The 2023 USDA Plant Hardiness Zone Map lists ZIP 20678 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.