Frost Dates for 59834 — Frenchtown, Montana

Half of springs at Alberton, MT see their last 32°F night by May 18; only one in ten is past it by May 5, and one in ten still has one after June 6. Planting tender crops after May 25 leaves a 30% risk of a frost on them, after May 30 20%, and after June 6 10%. The 19 days between the even-odds date and the one-in-ten date is wider than at 78% of the 68 Montana stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 25 in half of years, as early as September 7 one year in ten, and holds off past October 6 one year in ten. A hard freeze of 28°F follows 10 days later, around October 5; in spring the one-in-ten date for 28°F is May 15, 22 days before the 32°F one. The freeze-free season lasts 126 days in a typical year, shorter than at 50% of the 68 Montana stations; it reaches 146 days one year in ten and falls short of 104 one year in ten. On average 183 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 24 days longer, to about June 11, and return around September 9. Severe cold of 16°F or below comes every winter, usually between November 14 and March 8.

July is the warmest month at Alberton, MT, averaging 87°F by day and 49°F at night; December is the coldest at 33°F and 19°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, June still brings one in 17% of years.

Warmth for growing adds up to 1,814 growing degree days a year (base 50°F), fewer than at 56% of the 68 Montana stations. 25% of them (456) have built up by the end of June, and July adds the most, 550. Precipitation totals 18.7 inches a year, most in June (2.2") and least in July (0.9"); May to September bring 38% of it.

The nearest other station, Missoula 6 NW WFO, MT, 11 miles southeast of Frenchtown, has a last frost 12 days earlier (May 6), a first frost 9 days later (October 4), a season 25 days longer.

The first measurable snow (0.1 inch or more) in Frenchtown usually arrives around November 6, and the last of the season around April 5. Those are the middle dates across the winters of 1991–2020 at Alberton, MT, 11.2 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 59834 is 11 miles from Alberton, MT, which stands at 3,060 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 59834 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.