Frost Dates for 21047 — Fallston, Maryland

Half of springs at Aberdeen Phillips Field, MD see their last 32°F night by April 10; only one in ten is past it by March 27, and one in ten still has one after April 30. Planting tender crops after April 17 leaves a 30% risk of a frost on them, after April 22 20%, and after April 30 10%. The 20 days between the even-odds date and the one-in-ten date is wider than at 88% of the 50 Maryland stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 30 in half of years, as early as October 14 one year in ten, and holds off past November 12 one year in ten. A hard freeze of 28°F follows 11 days later, around November 10; in spring the one-in-ten date for 28°F is April 12, 18 days before the 32°F one. The freeze-free season lasts 201 days in a typical year, shorter than at 56% of the 50 Maryland stations; it reaches 221 days one year in ten and falls short of 178 one year in ten. On average 83 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 17 days longer, to about April 27, and return around October 19. Severe cold of 16°F or below comes in 99% of winters, usually between December 29 and February 23.

July is the warmest month at Aberdeen Phillips Field, MD, averaging 86°F by day and 68°F at night; January is the coldest at 42°F and 25°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 77% of years.

Warmth for growing adds up to 3,767 growing degree days a year (base 50°F), fewer than at 58% of the 50 Maryland stations. 34% of them (1,295) have built up by the end of June, and July adds the most, 838. Precipitation totals 47.2 inches a year, most in July (4.8") and least in February (2.8"); May to September bring 47% of it.

The nearest other station, Conowingo Dam, MD, 16 miles northeast of Fallston, has a last frost 7 days earlier (April 3), a first frost 7 days later (November 6), a season 16 days longer.

The first measurable snow (0.1 inch or more) in Fallston usually arrives around December 27, and the last of the season around February 26. Those are the middle dates across the winters of 1991–2020 at Aberdeen Phillips Field, MD, 14.1 miles away: half of years saw snow earlier, half later. Snow fell in 93% of those winters. The last 32°F night of spring typically comes 43 days after the last snow.

ZIP 21047 is 14 miles from Aberdeen Phillips Field, MD, which stands at 57 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 12 other ZIP codes share the station; its figures are presented in full for 21014 (Bel Air). The 2023 USDA Plant Hardiness Zone Map lists ZIP 21047 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.