Frost Dates for 83843 — Moscow, Idaho

Half of springs at Pullman Moscow Regional Airport, WA see their last 32°F night by April 29; only one in ten is past it by April 7, and one in ten still has one after May 14. Planting tender crops after May 5 leaves a 30% risk of a frost on them, after May 8 20%, and after May 14 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 2 in half of years, as early as September 17 one year in ten, and holds off past October 25 one year in ten. A hard freeze of 28°F follows 16 days later, around October 18; in spring the one-in-ten date for 28°F is April 27, 17 days before the 32°F one. The freeze-free season lasts 159 days in a typical year, longer than at 69% of the 67 Idaho stations; it reaches 187 days one year in ten and falls short of 133 one year in ten. On average 119 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 18, and return around September 19. Severe cold of 16°F or below comes in 98% of winters, usually between December 3 and February 9.

July is the warmest month at Pullman Moscow Regional Airport, WA, averaging 83°F by day and 51°F at night; December is the coldest at 37°F and 27°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 42% of years.

Warmth for growing adds up to 1,949 growing degree days a year (base 50°F), fewer than at 67% of the 67 Idaho stations. 26% of them (516) have built up by the end of June, and July adds the most, 527. Precipitation totals 17.7 inches a year, most in January (2.2") and least in July (0.4"); May to September bring 24% of it.

The nearest other station, Pullman 2 NW, WA, 10 miles west of Moscow, has a last frost 7 days later (May 6), a first frost 3 days earlier (September 29), a season 16 days shorter.

The first measurable snow (0.1 inch or more) in Moscow usually arrives around November 13, and the last of the season around April 5. Those are the middle dates across the winters of 1991–2020 at Moscow U Of I, 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 24 days after the last snow.

ZIP 83843 is 6 miles from Pullman Moscow Regional Airport, WA, which stands at 2,551 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83843 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.