Frost Dates for 21562 — Westernport, Maryland

Half of springs at Keyser 2 SSW, WV see their last 32°F night by April 30; only one in ten is past it by April 14, and one in ten still has one after May 19. Planting tender crops after May 7 leaves a 30% risk of a frost on them, after May 12 20%, and after May 19 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 15 in half of years, as early as October 1 one year in ten, and holds off past October 28 one year in ten. A hard freeze of 28°F follows 11 days later, around October 26; in spring the one-in-ten date for 28°F is May 4, 15 days before the 32°F one. The freeze-free season lasts 167 days in a typical year, shorter than at 94% of the 50 Maryland stations; it reaches 188 days one year in ten and falls short of 144 one year in ten. On average 127 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 May 12, and return around October 4. Severe cold of 16°F or below comes every winter, usually between December 1 and March 10.

July is the warmest month at Keyser 2 SSW, WV, averaging 89°F by day and 61°F at night; January is the coldest at 40°F and 21°F. A freezing night is all but certain in every month from October 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 45% of years.

Warmth for growing adds up to 3,299 growing degree days a year (base 50°F), fewer than at 82% of the 50 Maryland stations. 35% of them (1,144) have built up by the end of June, and July adds the most, 767. Precipitation totals 41.4 inches a year, most in May (4.5") and least in February (2.6"); May to September bring 47% of it.

The nearest other station, Savage Rvr Dam, MD, 6 miles west of Westernport and 530 feet higher, has a last frost 1 day earlier (April 29), a first frost 5 days later (October 20), a season 7 days longer.

The first measurable snow (0.1 inch or more) in Westernport usually arrives around November 25, and the last of the season around March 25. Those are the middle dates across the winters of 1991–2020 at Keyser 2 SSW, WV, 4.9 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 36 days after the last snow.

ZIP 21562 is 5 miles from Keyser 2 SSW, WV, which stands at 965 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 26726 (Keyser). The 2023 USDA Plant Hardiness Zone Map lists ZIP 21562 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.