Frost Dates for 01033 — Granby, Massachusetts

Half of springs at Belchertown, MA see their last 32°F night by May 3; only one in ten is past it by April 21, and one in ten still has one after May 16. Planting tender crops after May 8 leaves a 30% risk of a frost on them, after May 11 20%, and after May 16 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 51% of the 71 Massachusetts stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 14 in half of years, as early as October 1 one year in ten, and holds off past October 29 one year in ten. A hard freeze of 28°F follows 13 days later, around October 27; in spring the one-in-ten date for 28°F is May 4, 12 days before the 32°F one. The freeze-free season lasts 164 days in a typical year, shorter than at 59% of the 71 Massachusetts stations; it reaches 184 days one year in ten and falls short of 145 one year in ten. On average 143 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 10 days longer, to about May 13, and return around October 4. Severe cold of 16°F or below comes every winter, usually between December 1 and March 17.

July is the warmest month at Belchertown, MA, averaging 82°F by day and 60°F at night; January is the coldest at 33°F and 15°F. A freezing night is all but certain in every month from October 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 59% of years.

Warmth for growing adds up to 2,467 growing degree days a year (base 50°F), fewer than at 77% of the 71 Massachusetts stations. 30% of them (751) have built up by the end of June, and July adds the most, 645. Precipitation totals 47.6 inches a year, most in August (4.8") and least in February (3.1"); May to September bring 45% of it.

The nearest other station, Amherst, MA, 9 miles north of Granby and 405 feet lower, has a last frost 2 days later (May 5), a first frost 6 days earlier (October 8), a season 8 days shorter.

The first measurable snow (0.1 inch or more) in Granby usually arrives around November 30, and the last of the season around March 23. Those are the middle dates across the winters of 1991–2020 at Belchertown, MA, 8.9 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 41 days after the last snow.

ZIP 01033 is 9 miles from Belchertown, MA, which stands at 550 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 01056 (Ludlow). The 2023 USDA Plant Hardiness Zone Map lists ZIP 01033 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.