Billings climate

Billings Frost Dates and Growing Season

NOAA 1991-2020 normals for Billings Wtp, 2 km from Billings, elevation 3097 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Billings Wtp. 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 10 and the first fall freeze around October 1, a growing season of about 142 days.

Median at 36°F
last May 24, first September 21
Median at 32°F
last May 10, first October 1
Median at 28°F
last April 27, first October 12

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 7Jun 2May 30May 26May 24May 21May 18May 15May 10
32°FMay 24May 19May 15May 12May 10May 7May 4Apr 30Apr 26
28°FMay 10May 6May 3Apr 30Apr 27Apr 24Apr 21Apr 16Apr 10
24°FApr 30Apr 25Apr 21Apr 16Apr 13Apr 9Apr 5Apr 2Mar 28
20°FApr 18Apr 12Apr 8Apr 4Apr 1Mar 30Mar 25Mar 20Mar 13
16°FApr 8Apr 1Mar 30Mar 25Mar 22Mar 18Mar 13Mar 9Mar 3

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 7Sep 12Sep 15Sep 19Sep 21Sep 23Sep 26Sep 29Oct 3
32°FSep 19Sep 23Sep 26Sep 29Oct 1Oct 4Oct 6Oct 9Oct 15
28°FSep 27Oct 2Oct 5Oct 8Oct 12Oct 14Oct 17Oct 20Oct 24
24°FOct 6Oct 11Oct 16Oct 19Oct 22Oct 25Oct 28Oct 31Nov 4
20°FOct 15Oct 20Oct 25Oct 29Nov 1Nov 3Nov 6Nov 9Nov 16
16°FOct 24Oct 29Nov 2Nov 5Nov 8Nov 11Nov 15Nov 19Nov 24

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°F13813112612211811511110699
32°F161155150146142138134129121
28°F187179174170166162158153147
24°F212205200195190186181175168
20°F234227221216212208203197190
16°F255246240235231226220214208

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
6,955
Cooling degree days, base 65°F
488
Growing degree days, base 40°F
4,345
Growing degree days, base 45°F
3,254
Growing degree days, base 50°F
2,330
Growing degree days, base 55°F
1,564
Growing degree days, base 60°F
952

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,22600
February1,00901
March843010
April575049
May3268189
June10160412
July16210659
August31172607
September18336318
October549279
November89706
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 2 km from Billings. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00240802 (Billings Wtp). Public domain.