Frost Dates for 83641 — Melba, Idaho

Half of springs at Swan Falls Ph, ID see their last 32°F night by April 12; only one in ten is past it by March 23, and one in ten still has one after May 6. Planting tender crops after April 22 leaves a 30% risk of a frost on them, after April 28 20%, and after May 6 10%. The 24 days between the even-odds date and the one-in-ten date is wider than at 93% 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 26 in half of years, as early as October 9 one year in ten, and holds off past November 9 one year in ten. A hard freeze of 28°F follows 10 days later, around November 5; in spring the one-in-ten date for 28°F is April 25, 11 days before the 32°F one. The freeze-free season lasts 193 days in a typical year, longer than at 99% of the 67 Idaho stations; it reaches 219 days one year in ten and falls short of 162 one year in ten. On average 97 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 16 days longer, to about April 28, and return around October 15. Severe cold of 16°F or below comes in 97% of winters, usually between December 7 and January 30.

July is the warmest month at Swan Falls Ph, ID, averaging 95°F by day and 65°F at night; January is the coldest at 42°F and 26°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 73% of years and May still brings one in 17% of years.

Warmth for growing adds up to 3,721 growing degree days a year (base 50°F), the most of the 67 Idaho stations. 32% of them (1,188) have built up by the end of June, and July adds the most, 924. Precipitation totals 8.0 inches a year, most in May (1.3") and least in July (0.2"); May to September bring 33% of it.

The nearest other station, Nampa Sugar Factory, ID, 16 miles north of Melba, has a last frost 17 days later (April 29), a first frost 13 days earlier (October 13), a season 29 days shorter.

The first measurable snow (0.1 inch or more) in Melba usually arrives around December 5, and the last of the season around February 20. Those are the middle dates across the winters of 1991–2020 at Nampa Sugar Factory, ID, 16.1 miles away: half of years saw snow earlier, half later. Snow fell in 90% of those winters. The last 32°F night of spring typically comes 51 days after the last snow.

ZIP 83641 is 13 miles from Swan Falls Ph, ID, which stands at 2,325 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83641 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.