Frost Dates for 59011 — Big Timber, Montana

Half of springs at Big Timber, MT see their last 32°F night by May 14; only one in ten is past it by May 2, and one in ten still has one after May 27. Planting tender crops after May 20 leaves a 30% risk of a frost on them, after May 23 20%, and after May 27 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 74% of the 68 Montana stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 26 in half of years, as early as September 10 one year in ten, and holds off past October 8 one year in ten. A hard freeze of 28°F follows 9 days later, around October 5; in spring the one-in-ten date for 28°F is May 16, 11 days before the 32°F one. The freeze-free season lasts 133 days in a typical year, longer than at 63% of the 68 Montana stations; it reaches 150 days one year in ten and falls short of 114 one year in ten. On average 153 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 28, and return around September 13. Severe cold of 16°F or below comes every winter, usually between November 3 and March 27.

July is the warmest month at Big Timber, MT, averaging 86°F by day and 54°F at night; December is the coldest at 37°F and 20°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month.

Warmth for growing adds up to 2,118 growing degree days a year (base 50°F), more than at 71% of the 68 Montana stations. 27% of them (575) have built up by the end of June, and July adds the most, 615. Precipitation totals 17.0 inches a year, most in May (3.1") and least in January (0.7"); May to September bring 55% of it.

The nearest other station, Livingston Mission Field, MT, 28 miles southwest of Big Timber and 543 feet higher, has a last frost 13 days later (May 27), a first frost 12 days earlier (September 14), a season 25 days shorter.

The first measurable snow (0.1 inch or more) in Big Timber usually arrives around October 24, and the last of the season around March 27. Those are the middle dates across the winters of 1991–2020 at Big Timber, MT, 3.8 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 48 days after the last snow.

ZIP 59011 is 4 miles from Big Timber, MT, which stands at 4,100 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 59011 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.