Chouteau County climate

Chouteau County Frost Dates and Growing Season

NOAA 1991-2020 normals for Loma, 8 km from Chouteau County, elevation 2578 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Loma. 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 20 and the first fall freeze around September 19, a growing season of about 120 days.

Median at 36°F
last June 2, first September 7
Median at 32°F
last May 20, first September 19
Median at 28°F
last May 9, first September 29

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 21Jun 14Jun 10Jun 5Jun 2May 30May 28May 25May 20
32°FJun 3May 29May 26May 23May 20May 18May 15May 12May 8
28°FMay 21May 17May 14May 11May 9May 6May 3Apr 30Apr 25
24°FMay 9May 5May 2Apr 30Apr 28Apr 24Apr 20Apr 16Apr 10
20°FApr 30Apr 27Apr 22Apr 18Apr 14Apr 11Apr 8Apr 4Mar 30
16°FApr 23Apr 16Apr 12Apr 8Apr 5Apr 1Mar 29Mar 23Mar 17

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 22Aug 28Sep 1Sep 4Sep 7Sep 10Sep 13Sep 16Sep 21
32°FSep 4Sep 9Sep 13Sep 16Sep 19Sep 21Sep 24Sep 27Oct 2
28°FSep 16Sep 21Sep 24Sep 26Sep 29Oct 1Oct 4Oct 6Oct 11
24°FSep 24Sep 28Oct 1Oct 4Oct 6Oct 9Oct 12Oct 16Oct 20
20°FOct 1Oct 4Oct 8Oct 12Oct 15Oct 18Oct 21Oct 25Oct 29
16°FOct 9Oct 16Oct 20Oct 24Oct 27Oct 29Nov 1Nov 3Nov 9

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°F113106102989489847768
32°F13913212712412011611210699
28°F160154150146143139135131123
24°F184177172167162159155151145
20°F205198193188184180175169160
16°F228219213208203199193187180

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
7,741
Cooling degree days, base 65°F
413
Growing degree days, base 40°F
4,042
Growing degree days, base 45°F
3,002
Growing degree days, base 50°F
2,123
Growing degree days, base 55°F
1,398
Growing degree days, base 60°F
823

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,37501
February1,14101
March95806
April611035
May3446174
June12244374
July25185624
August46154574
September22123272
October618158
November97704
December1,30500

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 8 km from Chouteau County. 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 USC00245153 (Loma). Public domain.