Frost Dates for 83805 — Bonners Ferry, Idaho

Half of springs at Bonners Ferry, ID see their last 32°F night by April 30; only one in ten is past it by April 16, and one in ten still has one after May 16. Planting tender crops after May 6 leaves a 30% risk of a frost on them, after May 11 20%, and after May 16 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 66% 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 19 one year in ten. A hard freeze of 28°F follows 12 days later, around October 16; in spring the one-in-ten date for 28°F is April 30, 16 days before the 32°F one. The freeze-free season lasts 154 days in a typical year, longer than at 63% of the 67 Idaho stations; it reaches 174 days one year in ten and falls short of 132 one year in ten. On average 147 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 18 days longer, to about May 18, and return around September 22. Severe cold of 16°F or below comes every winter, usually between November 27 and February 28.

July is the warmest month at Bonners Ferry, ID, averaging 85°F by day and 53°F at night; December is the coldest at 33°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 48% of years.

Warmth for growing adds up to 2,078 growing degree days a year (base 50°F), fewer than at 57% of the 67 Idaho stations. 29% of them (608) have built up by the end of June, and July adds the most, 589. Precipitation totals 21.0 inches a year, most in December (3.2") and least in August (0.5"); May to September bring 28% of it.

The nearest other station, Troy, MT, 31 miles southeast of Bonners Ferry, has a last frost 14 days later (May 14), a first frost 9 days earlier (September 25), a season 22 days shorter.

The first measurable snow (0.1 inch or more) in Bonners Ferry usually arrives around November 21, and the last of the season around March 12. Those are the middle dates across the winters of 1991–2020 at Bonners Ferry, ID, 7.1 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 49 days after the last snow.

ZIP 83805 is 7 miles from Bonners Ferry, ID, which stands at 2,075 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 83805 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.