Frost Dates for 17257 — Shippensburg, Pennsylvania

Half of springs at Shippensburg, PA 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 6. Planting tender crops after April 25 leaves a 30% risk of a frost on them, after April 30 20%, and after May 6 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 50% of the 176 Pennsylvania stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 24 in half of years, as early as October 9 one year in ten, and holds off past November 6 one year in ten. A hard freeze of 28°F follows 11 days later, around November 4; in spring the one-in-ten date for 28°F is April 17, 19 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 207 days one year in ten and falls short of 166 one year in ten. On average 111 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 April 30, and return around October 11. Severe cold of 16°F or below comes every winter, usually between December 18 and March 4.

July is the warmest month at Shippensburg, PA, averaging 87°F by day and 64°F at night; January is the coldest at 38°F and 22°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 19% of years.

Warmth for growing adds up to 3,462 growing degree days a year (base 50°F), more than at 89% of the 176 Pennsylvania stations. 35% of them (1,215) have built up by the end of June, and July adds the most, 797. Precipitation totals 42.5 inches a year, most in September (4.3") and least in February (2.7"); May to September bring 46% of it.

The nearest other station, Chambersburg 1 ESE, PA, 11 miles southwest of Shippensburg, has a last frost 1 day earlier (April 18), a first frost 1 day later (October 25).

The first measurable snow (0.1 inch or more) in Shippensburg usually arrives around December 5, and the last of the season around March 19. Those are the middle dates across the winters of 1991–2020 at Shippensburg, PA, 0.9 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 31 days after the last snow.

ZIP 17257 is under a mile from Shippensburg, PA, which stands at 680 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 17257 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.