Frost Dates for 83660 — Parma, Idaho

Half of springs at Parma Exp Stn, ID see their last 32°F night by April 27; only one in ten is past it by April 13, and one in ten still has one after May 9. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 4 20%, and after May 9 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 99% of the 67 Idaho stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 9 in half of years, as early as September 26 one year in ten, and holds off past October 26 one year in ten. A hard freeze of 28°F follows 13 days later, around October 22; in spring the one-in-ten date for 28°F is April 28, 11 days before the 32°F one. The freeze-free season lasts 165 days in a typical year, longer than at 75% of the 67 Idaho stations; it reaches 185 days one year in ten and falls short of 146 one year in ten. On average 144 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 11 days longer, to about May 8, and return around September 28. Severe cold of 16°F or below comes every winter, usually between November 29 and February 14.

July is the warmest month at Parma Exp Stn, ID, averaging 92°F by day and 57°F at night; January is the coldest at 37°F and 23°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 34% of years.

Warmth for growing adds up to 2,912 growing degree days a year (base 50°F), more than at 84% of the 67 Idaho stations. 31% of them (907) have built up by the end of June, and July adds the most, 765. Precipitation totals 10.0 inches a year, most in May (1.4") and least in August (0.2"); May to September bring 33% of it.

The nearest other station, Nyssa, OR, 7 miles northwest of Parma, has a last frost 9 days earlier (April 18), a first frost 9 days later (October 18), a season 17 days longer.

The first measurable snow (0.1 inch or more) in Parma usually arrives around December 1, and the last of the season around February 14. Those are the middle dates across the winters of 1991–2020 at Parma Exp Stn, ID, 0.9 miles away: half of years saw snow earlier, half later. Snow fell in 91% of those winters. The last 32°F night of spring typically comes 72 days after the last snow.

ZIP 83660 is under a mile from Parma Exp Stn, ID, which stands at 2,290 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83660 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.