Frost Dates for 83861 — St Maries, Idaho

Half of springs at Saint Maries, ID see their last 32°F night by May 3; only one in ten is past it by April 20, and one in ten still has one after May 18. Planting tender crops after May 10 leaves a 30% risk of a frost on them, after May 13 20%, and after May 18 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 4 in half of years, as early as September 18 one year in ten, and holds off past October 20 one year in ten. A hard freeze of 28°F follows 15 days later, around October 19; in spring the one-in-ten date for 28°F is May 2, 16 days before the 32°F one. The freeze-free season lasts 152 days in a typical year, longer than at 61% of the 67 Idaho stations; it reaches 174 days one year in ten and falls short of 131 one year in ten. On average 138 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 17 days longer, to about May 20, and return around September 20. Severe cold of 16°F or below comes every winter, usually between December 1 and February 21.

July is the warmest month at Saint Maries, ID, averaging 84°F by day and 52°F at night; December is the coldest at 36°F and 24°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 63% of years.

Warmth for growing adds up to 1,995 growing degree days a year (base 50°F), fewer than at 63% of the 67 Idaho stations. 28% of them (550) have built up by the end of June, and July adds the most, 564. Precipitation totals 31.0 inches a year, most in January (4.4") and least in August (0.7"); May to September bring 23% of it.

The nearest other station, Potlatch 3 NNE, ID, 25 miles southwest of St Maries and 609 feet higher, has a last frost 12 days later (May 15), a first frost 13 days earlier (September 21), a season 26 days shorter.

The first measurable snow (0.1 inch or more) in St Maries usually arrives around November 17, and the last of the season around April 4. Those are the middle dates across the winters of 1991–2020 at Saint Maries, ID, 2.9 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 29 days after the last snow.

ZIP 83861 is 3 miles from Saint Maries, ID, which stands at 2,151 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83861 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.