Frost Dates for 20685 — Saint Leonard, Maryland

Half of springs at Solomons, MD see their last 32°F night by March 22; only one in ten is past it by March 6, and one in ten still has one after April 5. Planting tender crops after March 29 leaves a 30% risk of a frost on them, after April 1 20%, and after April 5 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 62% of the 50 Maryland stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 26 in half of years, as early as November 10 one year in ten, and holds off past December 12 one year in ten. A hard freeze of 28°F follows 13 days later, around December 9; in spring the one-in-ten date for 28°F is March 25, 11 days before the 32°F one. The freeze-free season lasts 248 days in a typical year, the longest of the 50 Maryland stations; it reaches 271 days one year in ten and falls short of 227 one year in ten. On average 59 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 3, and return around November 13. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 69%.

July is the warmest month at Solomons, MD, averaging 88°F by day and 73°F at night; January is the coldest at 45°F and 30°F. A freezing night is all but certain in every month from December to March (a 90% chance or more). From May to October the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 21% of years.

Warmth for growing adds up to 4,559 growing degree days a year (base 50°F), more than at 94% of the 50 Maryland stations. 35% of them (1,580) have built up by the end of June, and July adds the most, 939.

The nearest other station, Patuxent River NAS, MD, 11 miles southeast of Saint Leonard, has a last frost 7 days later (March 29), a first frost 11 days earlier (November 15), a season 18 days shorter.

The first measurable snow (0.1 inch or more) in Saint Leonard 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, 12.7 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 16 days after the last snow.

ZIP 20685 is 9 miles from Solomons, MD, which stands at 12 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 20657 (Lusby). The 2023 USDA Plant Hardiness Zone Map lists ZIP 20685 in zone 8a, the band where the coldest night of the year averaged 10 to 15°F (-12.2 to -9.4°C) over 1991–2020; a zone describes winter lows, not frost dates.