Frost Dates for 21619 — Chester, Maryland

Half of springs at Stevensville 2SW, MD see their last 32°F night by March 29; only one in ten is past it by March 15, and one in ten still has one after April 8. Planting tender crops after April 2 leaves a 30% risk of a frost on them, after April 4 20%, and after April 8 10%. The 10 days between the even-odds date and the one-in-ten date is the narrowest of the 50 Maryland stations behind this site's ZIP pages, so the end of frost is fairly predictable.

In fall the first 32°F night comes by November 12 in half of years, as early as October 29 one year in ten, and holds off past November 29 one year in ten. A hard freeze of 28°F follows 13 days later, around November 25; in spring the one-in-ten date for 28°F is March 31, 8 days before the 32°F one. The freeze-free season lasts 228 days in a typical year, longer than at 90% of the 50 Maryland stations; it reaches 250 days one year in ten and falls short of 209 one year in ten. On average 64 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 9 days longer, to about April 7, and return around November 1. Severe cold of 16°F or below comes in 95% of winters, usually between January 10 and February 11.

July is the warmest month at Stevensville 2SW, MD, averaging 87°F by day and 72°F at night; January is the coldest at 42°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 35% of years.

Warmth for growing adds up to 4,193 growing degree days a year (base 50°F), more than at 74% of the 50 Maryland stations. 34% of them (1,437) have built up by the end of June, and July adds the most, 913.

The nearest other station, Annapolis Naf, MD, 10 miles west of Chester, has a last frost 6 days earlier (March 23), a first frost 8 days later (November 20), a season 13 days longer.

The first measurable snow (0.1 inch or more) in Chester 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, 16.9 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 27 days after the last snow.

ZIP 21619 is 4 miles from Stevensville 2SW, MD, which stands at 10 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 21666 (Stevensville). The 2023 USDA Plant Hardiness Zone Map lists ZIP 21619 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.