Frost Dates for 18940 — Newtown, Pennsylvania

Half of springs at Trenton Mercer Co Airport, NJ see their last 32°F night by April 10; only one in ten is past it by March 30, and one in ten still has one after April 25. Planting tender crops after April 16 leaves a 30% risk of a frost on them, after April 20 20%, and after April 25 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 72% of the 176 Pennsylvania stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 1 in half of years, as early as October 15 one year in ten, and holds off past November 13 one year in ten. A hard freeze of 28°F follows 11 days later, around November 12; in spring the one-in-ten date for 28°F is April 12, 13 days before the 32°F one. The freeze-free season lasts 202 days in a typical year, longer than at 90% of the 176 Pennsylvania stations; it reaches 223 days one year in ten and falls short of 180 one year in ten. On average 97 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 15 days longer, to about April 25, and return around October 20. Severe cold of 16°F or below comes every winter, usually between December 25 and February 24.

July is the warmest month at Trenton Mercer Co Airport, NJ, averaging 86°F by day and 67°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 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 86% of years.

Warmth for growing adds up to 3,551 growing degree days a year (base 50°F), more than at 91% of the 176 Pennsylvania stations. 33% of them (1,189) have built up by the end of June, and July adds the most, 815. Precipitation totals 45.7 inches a year, most in June (4.4") and least in February (2.7"); May to September bring 46% of it.

The nearest other station, Neshaminy Falls, PA, 7 miles south of Newtown, has a last frost 11 days later (April 21), a first frost 7 days earlier (October 25), a season 17 days shorter.

The first measurable snow (0.1 inch or more) in Newtown usually arrives around December 6, and the last of the season around March 22. Those are the middle dates across the winters of 1991–2020 at Trenton Mercer Co Airport, NJ, 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 19 days after the last snow.

ZIP 18940 is 7 miles from Trenton Mercer Co Airport, NJ, which stands at 184 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 18940 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.