Frost Dates for 21756 — Keedysville, Maryland

Half of springs at Sharpsburg 5 S, MD see their last 32°F night by April 26; only one in ten is past it by April 11, and one in ten still has one after May 15. Planting tender crops after May 3 leaves a 30% risk of a frost on them, after May 8 20%, and after May 15 10%. The 19 days between the even-odds date and the one-in-ten date is wider than at 82% of the 50 Maryland stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 18 in half of years, as early as October 5 one year in ten, and holds off past November 2 one year in ten. A hard freeze of 28°F follows 12 days later, around October 30; in spring the one-in-ten date for 28°F is April 29, 16 days before the 32°F one. The freeze-free season lasts 175 days in a typical year, shorter than at 88% of the 50 Maryland stations; it reaches 195 days one year in ten and falls short of 153 one year in ten. On average 126 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 May 7, and return around October 9. Severe cold of 16°F or below comes every winter, usually between December 8 and March 7.

July is the warmest month at Sharpsburg 5 S, MD, averaging 86°F by day and 62°F at night; January is the coldest at 41°F and 21°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 35% of years.

Warmth for growing adds up to 3,306 growing degree days a year (base 50°F), fewer than at 80% of the 50 Maryland stations. 34% of them (1,136) have built up by the end of June, and July adds the most, 752. Precipitation totals 43.6 inches a year, most in May (4.6") and least in February (2.4"); May to September bring 48% of it.

The nearest other station, Hagerstown 1 E, MD, 12 miles north of Keedysville, has a last frost 15 days earlier (April 11), a first frost 10 days later (October 28), a season 24 days longer.

The first measurable snow (0.1 inch or more) in Keedysville usually arrives around December 13, and the last of the season around March 7. Those are the middle dates across the winters of 1991–2020 at Sharpsburg 5 S, MD, 4.6 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 21756 is 5 miles from Sharpsburg 5 S, MD, which stands at 400 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 6 other ZIP codes share the station; its figures are presented in full for 25425 (Harpers Ferry). The 2023 USDA Plant Hardiness Zone Map lists ZIP 21756 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.