Frost Dates for 83544 — Orofino, Idaho

Half of springs at Dworshak Fish Hatchery, ID see their last 32°F night by April 20; only one in ten is past it by April 1, and one in ten still has one after May 5. Planting tender crops after April 27 leaves a 30% risk of a frost on them, after May 1 20%, and after May 5 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 78% of the 67 Idaho stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 20 in half of years, as early as September 30 one year in ten, and holds off past November 7 one year in ten. A hard freeze of 28°F follows 13 days later, around November 2; in spring the one-in-ten date for 28°F is April 18, 17 days before the 32°F one. The freeze-free season lasts 182 days in a typical year, longer than at 94% of the 67 Idaho stations; it reaches 207 days one year in ten and falls short of 158 one year in ten. On average 101 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 15 days longer, to about May 5, and return around October 6. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 88%.

July is the warmest month at Dworshak Fish Hatchery, ID, averaging 90°F by day and 55°F at night; December is the coldest at 39°F and 28°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 88% of years and May still brings one in 20% of years.

Warmth for growing adds up to 2,671 growing degree days a year (base 50°F), more than at 69% of the 67 Idaho stations. 29% of them (787) have built up by the end of June, and July adds the most, 688. Precipitation totals 26.1 inches a year, most in November (3.2") and least in July (0.7"); May to September bring 25% of it.

The nearest other station, Kamiah, ID, 19 miles southeast of Orofino and 215 feet higher, has a last frost 9 days later (April 29), a first frost 15 days earlier (October 5), a season 19 days shorter.

The first measurable snow (0.1 inch or more) in Orofino usually arrives around December 10, and the last of the season around February 10. Those are the middle dates across the winters of 1991–2020 at Dworshak Fish Hatchery, ID, 5.9 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 69 days after the last snow.

ZIP 83544 is 6 miles from Dworshak Fish Hatchery, ID, which stands at 995 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83544 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.