Frost Dates for 83445 — Saint Anthony, Idaho

Half of springs at Saint Anthony, ID see their last 32°F night by May 17; only one in ten is past it by May 4, and one in ten still has one after June 10. Planting tender crops after May 25 leaves a 30% risk of a frost on them, after June 1 20%, and after June 10 10%. The 24 days between the even-odds date and the one-in-ten date is wider than at 93% of the 67 Idaho stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.

In fall the first 32°F night comes by September 22 in half of years, as early as September 5 one year in ten, and holds off past October 7 one year in ten. A hard freeze of 28°F follows 12 days later, around October 4; in spring the one-in-ten date for 28°F is May 17, 24 days before the 32°F one. The freeze-free season lasts 126 days in a typical year, shorter than at 73% of the 67 Idaho stations; it reaches 148 days one year in ten and falls short of 99 one year in ten. On average 206 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 22 days longer, to about June 8, and return around September 10. Severe cold of 16°F or below comes every winter, usually between November 5 and March 26.

July is the warmest month at Saint Anthony, ID, averaging 83°F by day and 50°F at night; January is the coldest at 28°F and 12°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 21% of years.

Warmth for growing adds up to 1,721 growing degree days a year (base 50°F), fewer than at 84% of the 67 Idaho stations. 25% of them (438) have built up by the end of June, and July adds the most, 524. Precipitation totals 14.9 inches a year, most in May (2.0") and least in August (0.6"); May to September bring 41% of it.

The nearest other station, Sugar City, ID, 5 miles south of Saint Anthony, has a last frost 12 days later (May 29), a first frost 9 days earlier (September 13), a season 20 days shorter.

The first measurable snow (0.1 inch or more) in Saint Anthony usually arrives around November 7, and the last of the season around April 3. Those are the middle dates across the winters of 1991–2020 at Saint Anthony, ID, 1.2 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 44 days after the last snow.

ZIP 83445 is 1 mile from Saint Anthony, ID, which stands at 4,910 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83445 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.