Frost Dates for 17028 — Grantville, Pennsylvania

Half of springs at Dehart Dam, PA see their last 32°F night by May 1; only one in ten is past it by April 15, and one in ten still has one after May 20. Planting tender crops after May 9 leaves a 30% risk of a frost on them, after May 14 20%, and after May 20 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 16 in half of years, as early as October 3 one year in ten, and holds off past November 1 one year in ten. A hard freeze of 28°F follows 14 days later, around October 30; in spring the one-in-ten date for 28°F is May 8, 12 days before the 32°F one. The freeze-free season lasts 168 days in a typical year, shorter than at 63% of the 176 Pennsylvania stations; it reaches 190 days one year in ten and falls short of 145 one year in ten. On average 128 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 May 12, and return around October 5. Severe cold of 16°F or below comes every winter, usually between December 9 and March 10.

July is the warmest month at Dehart Dam, PA, averaging 84°F by day and 60°F at night; January is the coldest at 37°F and 20°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 52% of years.

Warmth for growing adds up to 2,845 growing degree days a year (base 50°F), fewer than at 60% of the 176 Pennsylvania stations. 33% of them (944) have built up by the end of June, and July adds the most, 679. Precipitation totals 50.9 inches a year, most in September (5.6") and least in February (2.8"); May to September bring 48% of it.

The nearest other station, Lebanon 2 W, PA, 10 miles southeast of Grantville, has a last frost 11 days earlier (April 20), a first frost 9 days later (October 25), a season 17 days longer.

The first measurable snow (0.1 inch or more) in Grantville usually arrives around December 17, and the last of the season around March 28. Those are the middle dates across the winters of 1991–2020 at Dehart Dam, PA, 6.8 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 34 days after the last snow.

ZIP 17028 is 7 miles from Dehart Dam, PA, which stands at 537 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 6 other ZIP codes share the station; its figures are presented in full for 17032 (Halifax). The 2023 USDA Plant Hardiness Zone Map lists ZIP 17028 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.