Frost Dates for 83642 — Meridian, Idaho

Half of springs at Boise Air Terminal, ID see their last 32°F night by April 24; only one in ten is past it by April 4, and one in ten still has one after May 9. Planting tender crops after April 30 leaves a 30% risk of a frost on them, after May 4 20%, and after May 9 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 21 in half of years, as early as October 5 one year in ten, and holds off past November 5 one year in ten. A hard freeze of 28°F follows 10 days later, around October 31; in spring the one-in-ten date for 28°F is April 25, 14 days before the 32°F one. The freeze-free season lasts 179 days in a typical year, longer than at 91% of the 67 Idaho stations; it reaches 203 days one year in ten and falls short of 156 one year in ten. On average 108 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 8, and return around October 8. Severe cold of 16°F or below comes in 98% of winters, usually between December 7 and February 2.

July is the warmest month at Boise Air Terminal, ID, averaging 93°F by day and 62°F at night; December is the coldest at 39°F and 25°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 29% of years.

Warmth for growing adds up to 3,290 growing degree days a year (base 50°F), more than at 97% of the 67 Idaho stations. 30% of them (981) have built up by the end of June, and July adds the most, 846. Precipitation totals 11.5 inches a year, most in May (1.5") and least in July (0.2"); May to September bring 27% of it.

The nearest other station, Nampa Sugar Factory, ID, 9 miles west of Meridian and 344 feet lower, has a last frost 5 days later (April 29), a first frost 8 days earlier (October 13), a season 15 days shorter.

The first measurable snow (0.1 inch or more) in Meridian 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, 8.3 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 40 days after the last snow.

ZIP 83642 is 8 miles from Boise Air Terminal, ID, which stands at 2,814 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 9 other ZIP codes share the station; its figures are presented in full for 83709 (Boise). The 2023 USDA Plant Hardiness Zone Map lists ZIP 83642 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.