Frost Dates for 83467 — Salmon, Idaho

Half of springs at Salmon-Ksra, ID see their last 32°F night by May 17; only one in ten is past it by May 3, and one in ten still has one after June 9. Planting tender crops after May 25 leaves a 30% risk of a frost on them, after May 31 20%, and after June 9 10%. The 23 days between the even-odds date and the one-in-ten date is wider than at 87% 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 24 in half of years, as early as September 9 one year in ten, and holds off past October 5 one year in ten. A hard freeze of 28°F follows 11 days later, around October 5; in spring the one-in-ten date for 28°F is May 19, 21 days before the 32°F one. The freeze-free season lasts 127 days in a typical year, shorter than at 72% of the 67 Idaho stations; it reaches 145 days one year in ten and falls short of 100 one year in ten. On average 180 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 21 days longer, to about June 7, and return around September 13. Severe cold of 16°F or below comes every winter, usually between November 8 and March 9.

July is the warmest month at Salmon-Ksra, ID, averaging 86°F by day and 52°F at night; January is the coldest at 28°F and 11°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 20% of years.

Warmth for growing adds up to 1,911 growing degree days a year (base 50°F), fewer than at 72% of the 67 Idaho stations. 28% of them (530) have built up by the end of June, and July adds the most, 587. Precipitation totals 9.6 inches a year, most in June (1.6") and least in February (0.4"); May to September bring 53% of it.

The first measurable snow (0.1 inch or more) in Salmon usually arrives around November 25, and the last of the season around March 6. Those are the middle dates across the winters of 1991–2020 at Salmon-Ksra, ID, 5 miles away: half of years saw snow earlier, half later. Snow fell in 97% of those winters. The last 32°F night of spring typically comes 72 days after the last snow.

ZIP 83467 is 5 miles from Salmon-Ksra, ID, which stands at 3,953 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83467 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.