Frost Dates for 83338 — Jerome, Idaho

Half of springs at Jerome Co Airport, ID see their last 32°F night by May 1; only one in ten is past it by April 17, and one in ten still has one after May 16. Planting tender crops after May 7 leaves a 30% risk of a frost on them, after May 11 20%, and after May 16 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 14 in half of years, as early as September 29 one year in ten, and holds off past October 28 one year in ten. A hard freeze of 28°F follows 12 days later, around October 26; in spring the one-in-ten date for 28°F is May 3, 13 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 186 days one year in ten and falls short of 144 one year in ten. On average 142 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 14 days longer, to about May 15, and return around October 1. Severe cold of 16°F or below comes every winter, usually between November 26 and February 18.

July is the warmest month at Jerome Co Airport, ID, averaging 90°F by day and 59°F at night; January is the coldest at 36°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 53% of years.

Warmth for growing adds up to 2,738 growing degree days a year (base 50°F), more than at 76% of the 67 Idaho stations. 28% of them (775) have built up by the end of June, and July adds the most, 749. Precipitation totals 9.9 inches a year, most in May (1.4") and least in July (0.1"); May to September bring 27% of it.

The nearest other station, Jerome, ID, 3 miles northwest of Jerome and 308 feet lower, has a last frost 1 day later (May 2), the same first-frost date, a season 1 day longer.

The first measurable snow (0.1 inch or more) in Jerome usually arrives around November 22, and the last of the season around March 28. Those are the middle dates across the winters of 1991–2020 at Twin Falls 6 E, ID, 12.8 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 34 days after the last snow.

ZIP 83338 is 1 mile from Jerome Co Airport, ID, which stands at 4,048 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83338 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.