Frost Dates for 01464 — Shirley, Massachusetts

Half of springs at Fitchburg Municipal Airport, MA see their last 32°F night by April 29; only one in ten is past it by April 19, and one in ten still has one after May 13. Planting tender crops after May 4 leaves a 30% risk of a frost on them, after May 8 20%, and after May 13 10%. The 14 days between the even-odds date and the one-in-ten date is wider than at 51% of the 71 Massachusetts stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 11 in half of years, as early as October 1 one year in ten, and holds off past October 27 one year in ten. A hard freeze of 28°F follows 12 days later, around October 23; in spring the one-in-ten date for 28°F is April 29, 14 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 183 days one year in ten and falls short of 147 one year in ten. On average 137 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 9, and return around October 1. Severe cold of 16°F or below comes every winter, usually between November 29 and March 16.

July is the warmest month at Fitchburg Municipal Airport, MA, averaging 83°F by day and 62°F at night; January is the coldest at 34°F and 16°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 43% of years.

Warmth for growing adds up to 2,701 growing degree days a year (base 50°F), more than at 54% of the 71 Massachusetts stations. 31% of them (848) have built up by the end of June, and July adds the most, 696. Precipitation totals 43.5 inches a year, most in October (4.5") and least in January (2.7"); May to September bring 43% of it.

The nearest other station, Fitchburg Coop, MA, 9 miles northwest of Shirley and 317 feet higher, has a last frost 2 days later (May 1), a first frost 2 days earlier (October 9), a season 2 days shorter.

The first measurable snow (0.1 inch or more) in Shirley usually arrives around November 15, and the last of the season around April 10. Those are the middle dates across the winters of 1991–2020 at Ashburnham, MA, 14.3 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 19 days after the last snow.

ZIP 01464 is 6 miles from Fitchburg Municipal Airport, MA, which stands at 348 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 7 other ZIP codes share the station; its figures are presented in full for 01453 (Leominster). The 2023 USDA Plant Hardiness Zone Map lists ZIP 01464 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.