Billings climate

Billings Frost Dates and Growing Season

NOAA 1991-2020 normals for Billings, 0.3 km from Billings, elevation 1000 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Billings. 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 15 and the first fall freeze around October 26, a growing season of about 194 days.

Median at 36°F
last April 25, first October 17
Median at 32°F
last April 15, first October 26
Median at 28°F
last April 2, first November 4

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°FMay 7May 3Apr 30Apr 28Apr 25Apr 21Apr 18Apr 15Apr 10
32°FMay 1Apr 26Apr 22Apr 18Apr 15Apr 11Apr 7Apr 2Mar 29
28°FApr 19Apr 13Apr 9Apr 5Apr 2Mar 30Mar 26Mar 21Mar 15
24°FApr 6Apr 1Mar 28Mar 25Mar 20Mar 16Mar 12Mar 7Mar 2
20°FMar 25Mar 19Mar 14Mar 10Mar 7Mar 4Mar 1Feb 25Feb 19
16°FMar 15Mar 9Mar 4Mar 1Feb 27Feb 22Feb 17Feb 10Jan 31

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°FOct 1Oct 7Oct 12Oct 15Oct 17Oct 20Oct 23Oct 26Oct 31
32°FOct 12Oct 17Oct 21Oct 23Oct 26Oct 29Nov 1Nov 4Nov 9
28°FOct 20Oct 26Oct 30Nov 1Nov 4Nov 7Nov 11Nov 15Nov 21
24°FOct 29Nov 2Nov 6Nov 9Nov 13Nov 16Nov 21Nov 26Dec 1
20°FNov 4Nov 10Nov 14Nov 19Nov 23Nov 28Dec 2Dec 6Dec 13
16°FNov 14Nov 22Nov 27Dec 1Dec 6Dec 10Dec 15Dec 21Dec 30

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°F196190184179175172168163156
32°F216208203198194190186180172
28°F239231225219214211206201192
24°F263254248244238233228221211
20°F286276271266261256250245237
16°F316304297290285279273267257

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
4,153
Cooling degree days, base 65°F
1,841
Growing degree days, base 40°F
7,432
Growing degree days, base 45°F
6,030
Growing degree days, base 50°F
4,773
Growing degree days, base 55°F
3,654
Growing degree days, base 60°F
2,679

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January93807
February731023
March5275108
April26329255
May76138529
June3362808
July0521986
August0481945
September28247669
October20954336
November522595
December856012

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 0.3 km from Billings. 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 USC00340755 (Billings). Public domain.