Frost Dates for 83648 — Mountain Home Afb, Idaho

Half of springs at Mountain Home, ID see their last 32°F night by May 2; only one in ten is past it by April 18, and one in ten still has one after May 23. Planting tender crops after May 10 leaves a 30% risk of a frost on them, after May 15 20%, and after May 23 10%. The 21 days between the even-odds date and the one-in-ten date is wider than at 78% of the 67 Idaho stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.

In fall the first 32°F night comes by October 8 in half of years, as early as September 25 one year in ten, and holds off past October 24 one year in ten. A hard freeze of 28°F follows 12 days later, around October 20; in spring the one-in-ten date for 28°F is May 8, 15 days before the 32°F one. The freeze-free season lasts 157 days in a typical year, longer than at 67% of the 67 Idaho stations; it reaches 180 days one year in ten and falls short of 131 one year in ten. On average 139 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 17, and return around September 28. Severe cold of 16°F or below comes every winter, usually between November 25 and February 19.

July is the warmest month at Mountain Home, ID, averaging 95°F by day and 60°F at night; December is the coldest at 39°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 54% of years.

Warmth for growing adds up to 3,171 growing degree days a year (base 50°F), more than at 93% of the 67 Idaho stations. 30% of them (937) have built up by the end of June, and July adds the most, 846.

The nearest other station, Swan Falls Ph, ID, 29 miles northwest of Mountain Home Afb and 815 feet lower, has a last frost 20 days earlier (April 12), a first frost 18 days later (October 26), a season 36 days longer.

The first measurable snow (0.1 inch or more) in Mountain Home Afb usually arrives around November 21, and the last of the season around March 15. Those are the middle dates across the winters of 1991–2020 at Boise Air Terminal, ID, 39.5 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 48 days after the last snow.

ZIP 83648 is 8 miles from Mountain Home, ID, which stands at 3,140 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 83647 (Mountain Home). The 2023 USDA Plant Hardiness Zone Map lists ZIP 83648 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.