Frost Dates for 83539 — Kooskia, Idaho

Half of springs at Lowell Three Rivers, ID see their last 32°F night by April 16; only one in ten is past it by March 26, and one in ten still has one after May 4. Planting tender crops after April 25 leaves a 30% risk of a frost on them, after April 30 20%, and after May 4 10%. The 18 days between the even-odds date and the one-in-ten date is narrower than at 42% of the 67 Idaho stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 25 in half of years, as early as October 5 one year in ten, and holds off past November 13 one year in ten. A hard freeze of 28°F follows 16 days later, around November 10; in spring the one-in-ten date for 28°F is April 9, 25 days before the 32°F one. The freeze-free season lasts 191 days in a typical year, longer than at 97% of the 67 Idaho stations; it reaches 220 days one year in ten and falls short of 163 one year in ten. On average 95 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 19 days longer, to about May 5, and return around October 8. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 85%.

July is the warmest month at Lowell Three Rivers, ID, averaging 92°F by day and 55°F at night; December is the coldest at 38°F and 29°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 77% of years and May still brings one in 19% of years.

Warmth for growing adds up to 2,712 growing degree days a year (base 50°F), more than at 73% of the 67 Idaho stations. 29% of them (790) have built up by the end of June, and July adds the most, 730. Precipitation totals 39.6 inches a year, most in November (5.0") and least in July (0.6"); May to September bring 23% of it.

The nearest other station, Kamiah, ID, 17 miles northwest of Kooskia and 270 feet lower, has a last frost 13 days later (April 29), a first frost 20 days earlier (October 5), a season 28 days shorter.

The first measurable snow (0.1 inch or more) in Kooskia usually arrives around November 27, and the last of the season around March 6. Those are the middle dates across the winters of 1991–2020 at Fenn Rs, ID, 9.3 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 41 days after the last snow.

ZIP 83539 is 6 miles from Lowell Three Rivers, ID, which stands at 1,480 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83539 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.