Frost Dates for 21655 — Preston, Maryland

Half of springs at Royal Oak 2 SSW, MD see their last 32°F night by April 1; only one in ten is past it by March 18, and one in ten still has one after April 15. Planting tender crops after April 7 leaves a 30% risk of a frost on them, after April 10 20%, and after April 15 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 7 in half of years, as early as October 24 one year in ten, and holds off past November 23 one year in ten. A hard freeze of 28°F follows 13 days later, around November 20; in spring the one-in-ten date for 28°F is April 1, 14 days before the 32°F one. The freeze-free season lasts 220 days in a typical year, longer than at 78% of the 50 Maryland stations; it reaches 240 days one year in ten and falls short of 202 one year in ten. On average 69 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 14 days longer, to about April 15, and return around October 29. Severe cold of 16°F or below comes in 91% of winters, usually between January 8 and February 8.

July is the warmest month at Royal Oak 2 SSW, MD, averaging 88°F by day and 70°F at night; January is the coldest at 45°F and 29°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 51% of years.

Warmth for growing adds up to 4,342 growing degree days a year (base 50°F), more than at 80% of the 50 Maryland stations. 36% of them (1,548) have built up by the end of June, and July adds the most, 902. Precipitation totals 47.7 inches a year, most in August (4.8") and least in February (3.1"); May to September bring 45% of it.

The nearest other station, Vienna, MD, 19 miles south of Preston, has a last frost 7 days later (April 8), a first frost 3 days earlier (November 4), a season 11 days shorter.

The first measurable snow (0.1 inch or more) in Preston usually arrives around December 28, and the last of the season around March 2. Those are the middle dates across the winters of 1991–2020 at Royal Oak 2 SSW, MD, 15.1 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 30 days after the last snow.

ZIP 21655 is 15 miles from Royal Oak 2 SSW, MD, which stands at 10 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 21601 (Easton). The 2023 USDA Plant Hardiness Zone Map lists ZIP 21655 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.