Frost Dates for 17345 — Manchester, Pennsylvania

Half of springs at Middletown Harrisburg International Airport, PA see their last 32°F night by April 9; only one in ten is past it by March 28, and one in ten still has one after April 25. Planting tender crops after April 15 leaves a 30% risk of a frost on them, after April 18 20%, and after April 25 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 51% of the 176 Pennsylvania stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 2 in half of years, as early as October 18 one year in ten, and holds off past November 15 one year in ten. A hard freeze of 28°F follows 12 days later, around November 14; in spring the one-in-ten date for 28°F is April 9, 16 days before the 32°F one. The freeze-free season lasts 206 days in a typical year, longer than at 94% of the 176 Pennsylvania stations; it reaches 224 days one year in ten and falls short of 185 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 14 days longer, to about April 23, and return around October 22. Severe cold of 16°F or below comes every winter, usually between December 26 and February 25.

July is the warmest month at Middletown Harrisburg International Airport, PA, averaging 87°F by day and 68°F at night; January is the coldest at 39°F and 23°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 81% of years.

Warmth for growing adds up to 3,702 growing degree days a year (base 50°F), more than at 94% of the 176 Pennsylvania stations. 35% of them (1,281) have built up by the end of June, and July adds the most, 846. Precipitation totals 44.2 inches a year, most in September (4.8") and least in February (2.6"); May to September bring 48% of it.

The nearest other station, York 3 SSW Pump Stn, PA, 10 miles south of Manchester, has a last frost 17 days later (April 26), a first frost 14 days earlier (October 19), a season 29 days shorter.

The first measurable snow (0.1 inch or more) in Manchester usually arrives around January 7, and the last of the season around March 9. Those are the middle dates across the winters of 1991–2020 at York Haven, PA, 3.3 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 17345 is 9 miles from Middletown Harrisburg International Airport, PA, which stands at 312 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 9 other ZIP codes share the station; its figures are presented in full for 17022 (Elizabethtown). The 2023 USDA Plant Hardiness Zone Map lists ZIP 17345 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.