Frost Dates for 07834 — Denville, New Jersey

Half of springs at Boonton 1 SE, NJ see their last 32°F night by April 17; 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 24 leaves a 30% risk of a frost on them, after April 30 20%, and after May 5 10%. The 18 days between the even-odds date and the one-in-ten date is wider than at 80% of the 56 New Jersey stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 23 in half of years, as early as October 8 one year in ten, and holds off past November 6 one year in ten. A hard freeze of 28°F follows 10 days later, around November 2; 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 189 days in a typical year, shorter than at 59% of the 56 New Jersey stations; it reaches 209 days one year in ten and falls short of 166 one year in ten. On average 124 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 May 1, and return around October 12. Severe cold of 16°F or below comes every winter, usually between December 11 and March 6.

July is the warmest month at Boonton 1 SE, NJ, averaging 85°F by day and 64°F at night; January is the coldest at 38°F and 21°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 17% of years.

Warmth for growing adds up to 3,151 growing degree days a year (base 50°F), fewer than at 82% of the 56 New Jersey stations. 33% of them (1,025) have built up by the end of June, and July adds the most, 766. Precipitation totals 49.3 inches a year, most in June (4.9") and least in February (2.8"); May to September bring 45% of it.

The nearest other station, Charlotteburg Rsvr, NJ, 10 miles north of Denville and 498 feet higher, has a last frost 8 days later (April 25), a first frost 6 days earlier (October 17), a season 15 days shorter.

The first measurable snow (0.1 inch or more) in Denville usually arrives around December 17, and the last of the season around March 5. Those are the middle dates across the winters of 1991–2020 at Boonton 1 SE, NJ, 4.7 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 43 days after the last snow.

ZIP 07834 is 5 miles from Boonton 1 SE, NJ, which stands at 280 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 15 other ZIP codes share the station; its figures are presented in full for 07054 (Parsippany). The 2023 USDA Plant Hardiness Zone Map lists ZIP 07834 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.