Bigfork climate

Bigfork Frost Dates and Growing Season

NOAA 1991-2020 normals for Creston, 14.6 km from Bigfork, elevation 2935 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Creston. 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 May 12 and the first fall freeze around September 25, a growing season of about 134 days.

Median at 36°F
last May 30, first September 8
Median at 32°F
last May 12, first September 25
Median at 28°F
last April 28, first October 5

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 16Jun 9Jun 5Jun 1May 30May 27May 24May 20May 16
32°FMay 26May 21May 18May 15May 12May 10May 7May 4Apr 30
28°FMay 11May 7May 4May 1Apr 28Apr 25Apr 21Apr 16Apr 10
24°FApr 26Apr 20Apr 15Apr 12Apr 8Apr 4Apr 2Mar 30Mar 21
20°FApr 13Apr 6Apr 2Mar 31Mar 26Mar 21Mar 15Mar 10Mar 5
16°FApr 1Mar 26Mar 20Mar 14Mar 10Mar 7Mar 3Feb 28Feb 21

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°FAug 25Aug 30Sep 3Sep 5Sep 8Sep 13Sep 16Sep 20Sep 25
32°FSep 9Sep 16Sep 20Sep 23Sep 25Sep 27Sep 30Oct 3Oct 8
28°FSep 23Sep 27Oct 1Oct 3Oct 5Oct 9Oct 12Oct 16Oct 22
24°FOct 1Oct 5Oct 9Oct 14Oct 18Oct 22Oct 26Oct 29Nov 4
20°FOct 10Oct 17Oct 22Oct 27Oct 31Nov 3Nov 7Nov 13Nov 22
16°FOct 21Oct 29Nov 1Nov 6Nov 11Nov 16Nov 21Nov 26Dec 1

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°F12311511010510197908678
32°F154146142138134131127122114
28°F182175169165161157153148139
24°F214207202195191186181175168
20°F247238231226220215209201192
16°F271262255249244239234225216

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
7,666
Cooling degree days, base 65°F
192
Growing degree days, base 40°F
3,347
Growing degree days, base 45°F
2,378
Growing degree days, base 50°F
1,586
Growing degree days, base 55°F
951
Growing degree days, base 60°F
489

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,22900
February1,04000
March91800
April641018
May3893133
June20817266
July6393495
August7875463
September2935187
October665024
November94401
December1,20000

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 14.6 km from Bigfork. 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 USC00242104 (Creston). Public domain.