Frost Dates for 59101 — Billings, Montana

Half of springs at Billings Wtp, MT see their last 32°F night by May 10; only one in ten is past it by April 26, and one in ten still has one after May 24. Planting tender crops after May 15 leaves a 30% risk of a frost on them, after May 19 20%, and after May 24 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 60% of the 68 Montana stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 1 in half of years, as early as September 19 one year in ten, and holds off past October 15 one year in ten. A hard freeze of 28°F follows 11 days later, around October 12; in spring the one-in-ten date for 28°F is May 10, 14 days before the 32°F one. The freeze-free season lasts 142 days in a typical year, longer than at 78% of the 68 Montana stations; it reaches 161 days one year in ten and falls short of 121 one year in ten. On average 157 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 24, and return around September 21. Severe cold of 16°F or below comes every winter, usually between November 8 and March 22.

July is the warmest month at Billings Wtp, MT, averaging 86°F by day and 56°F at night; January is the coldest at 37°F and 14°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 80% of years.

Warmth for growing adds up to 2,330 growing degree days a year (base 50°F), more than at 87% of the 68 Montana stations. 28% of them (661) have built up by the end of June, and July adds the most, 659. Precipitation totals 15.6 inches a year, most in May (2.5") and least in January (0.6"); May to September bring 55% of it.

The nearest other station, Billings WFO, MT, 4 miles west of Billings, has a last frost 5 days earlier (May 5), a first frost 2 days later (October 3), a season 7 days longer.

The first measurable snow (0.1 inch or more) in Billings usually arrives around October 21, and the last of the season around April 22. Those are the middle dates across the winters of 1991–2020 at Billings WFO, MT, 4.1 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 18 days after the last snow.

ZIP 59101 is 2 miles from Billings Wtp, MT, which stands at 3,097 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 59101 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.