Bonners Ferry climate

Bonners Ferry Frost Dates and Growing Season

NOAA 1991-2020 normals for Bonners Ferry, 0.5 km from Bonners Ferry, elevation 2075 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bonners Ferry. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around April 30 and the first fall freeze around October 4, a growing season of about 154 days.

Median at 36°F
last May 18, first September 22
Median at 32°F
last April 30, first October 4
Median at 28°F
last April 10, first October 16

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FJun 8May 31May 26May 22May 18May 14May 10May 6May 1
32°FMay 16May 11May 6May 3Apr 30Apr 28Apr 25Apr 21Apr 16
28°FApr 30Apr 24Apr 18Apr 14Apr 10Apr 6Apr 3Mar 31Mar 26
24°FApr 6Mar 31Mar 28Mar 24Mar 20Mar 16Mar 12Mar 8Mar 3
20°FMar 23Mar 16Mar 12Mar 8Mar 5Mar 3Feb 28Feb 24Feb 17
16°FMar 15Mar 9Mar 5Mar 2Feb 28Feb 24Feb 19Feb 11Jan 30

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FSep 5Sep 10Sep 15Sep 19Sep 22Sep 25Sep 28Oct 2Oct 6
32°FSep 18Sep 23Sep 27Oct 1Oct 4Oct 7Oct 10Oct 14Oct 19
28°FSep 28Oct 3Oct 8Oct 12Oct 16Oct 20Oct 24Oct 29Nov 5
24°FOct 6Oct 16Oct 21Oct 25Oct 30Nov 3Nov 7Nov 13Nov 23
20°FOct 20Oct 30Nov 3Nov 8Nov 13Nov 18Nov 24Nov 29Dec 7
16°FNov 1Nov 9Nov 17Nov 23Nov 27Dec 1Dec 6Dec 12Dec 23

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F14613913412912411911310696
32°F174168162158154149145139132
28°F211202196191186182176169160
24°F248239232227221216210204194
20°F282273264258252246240232222
16°F310298289282275268260253242

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
6,674
Cooling degree days, base 65°F
355
Growing degree days, base 40°F
4,045
Growing degree days, base 45°F
2,972
Growing degree days, base 50°F
2,078
Growing degree days, base 55°F
1,340
Growing degree days, base 60°F
756

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,12500
February93500
March80501
April530038
May2798211
June13037358
July31155589
August33137569
September20219275
October591036
November88201
December1,13300

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 0.5 km from Bonners Ferry. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00101079 (Bonners Ferry). Public domain.