Frost Dates for 17520 — East Petersburg, Pennsylvania

Half of springs at Lancaster Airport, PA see their last 32°F night by April 18; only one in ten is past it by April 4, and one in ten still has one after May 5. Planting tender crops after April 25 leaves a 30% risk of a frost on them, after April 30 20%, and after May 5 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 25 in half of years, as early as October 10 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 5; in spring the one-in-ten date for 28°F is April 18, 17 days before the 32°F one. The freeze-free season lasts 186 days in a typical year, longer than at 72% of the 176 Pennsylvania stations; it reaches 207 days one year in ten and falls short of 166 one year in ten. On average 109 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 1, and return around October 14. Severe cold of 16°F or below comes every winter, usually between December 18 and March 4.

July is the warmest month at Lancaster Airport, PA, averaging 86°F by day and 65°F at night; January is the coldest at 40°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 18% of years.

Warmth for growing adds up to 3,426 growing degree days a year (base 50°F), more than at 88% of the 176 Pennsylvania stations. 34% of them (1,175) have built up by the end of June, and July adds the most, 787. Precipitation totals 42.0 inches a year, most in June (4.8") and least in February (2.2"); May to September bring 49% of it.

The nearest other station, Landisville 2 NW, PA, 4 miles west of East Petersburg, has a last frost 12 days later (April 30), a first frost 15 days earlier (October 10), a season 24 days shorter.

The first measurable snow (0.1 inch or more) in East Petersburg usually arrives around December 10, and the last of the season around March 19. Those are the middle dates across the winters of 1991–2020 at Landisville 2 NW, PA, 4.2 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 30 days after the last snow.

ZIP 17520 is 3 miles from Lancaster Airport, PA, which stands at 403 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 17543 (Lititz). The 2023 USDA Plant Hardiness Zone Map lists ZIP 17520 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.