Frost Dates for 17361 — Shrewsbury, Pennsylvania

Half of springs at Millers 4 NE, MD see their last 32°F night by April 19; only one in ten is past it by April 4, and one in ten still has one after May 8. Planting tender crops after April 26 leaves a 30% risk of a frost on them, after May 1 20%, and after May 8 10%. The 19 days between the even-odds date and the one-in-ten date is wider than at 90% of the 176 Pennsylvania stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 25 in half of years, as early as October 8 one year in ten, and holds off past November 7 one year in ten. A hard freeze of 28°F follows 10 days later, around November 4; in spring the one-in-ten date for 28°F is April 21, 17 days before the 32°F one. The freeze-free season lasts 188 days in a typical year, longer than at 76% of the 176 Pennsylvania stations; it reaches 208 days one year in ten and falls short of 163 one year in ten. On average 101 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 13 days longer, to about May 2, and return around October 13. Severe cold of 16°F or below comes every winter, usually between December 16 and March 5.

July is the warmest month at Millers 4 NE, MD, averaging 85°F by day and 64°F at night; January is the coldest at 40°F and 24°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 21% of years.

Warmth for growing adds up to 3,441 growing degree days a year (base 50°F), more than at 88% of the 176 Pennsylvania stations. 35% of them (1,207) have built up by the end of June, and July adds the most, 764. Precipitation totals 47.8 inches a year, most in September (5.1") and least in February (2.9"); May to September bring 46% of it.

The nearest other station, York 3 SSW Pump Stn, PA, 11 miles north of Shrewsbury and 470 feet lower, has a last frost 7 days later (April 26), a first frost 6 days earlier (October 19), a season 11 days shorter.

The first measurable snow (0.1 inch or more) in Shrewsbury usually arrives around December 3, and the last of the season around March 29. Those are the middle dates across the winters of 1991–2020 at Millers 4 NE, MD, 7.4 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 21 days after the last snow.

ZIP 17361 is 7 miles from Millers 4 NE, MD, which stands at 860 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 21074 (Hampstead). The 2023 USDA Plant Hardiness Zone Map lists ZIP 17361 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.