Dawson County climate

Dawson County Frost Dates and Growing Season

NOAA 1991-2020 normals for Glendive, 22.5 km from Dawson County, elevation 2075 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Glendive. 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 3 and the first fall freeze around October 4, a growing season of about 153 days.

Median at 36°F
last May 14, first September 26
Median at 32°F
last May 3, first October 4
Median at 28°F
last April 24, first October 13

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 27May 22May 19May 16May 14May 11May 8May 5May 2
32°FMay 16May 12May 8May 6May 3May 1Apr 29Apr 24Apr 19
28°FMay 8May 3Apr 30Apr 27Apr 24Apr 21Apr 18Apr 14Apr 9
24°FApr 29Apr 24Apr 19Apr 16Apr 12Apr 9Apr 6Apr 3Mar 30
20°FApr 19Apr 14Apr 10Apr 7Apr 4Apr 2Mar 30Mar 24Mar 16
16°FApr 11Apr 6Apr 3Mar 30Mar 26Mar 22Mar 17Mar 12Mar 7

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 12Sep 18Sep 21Sep 23Sep 26Sep 28Sep 30Oct 3Oct 7
32°FSep 22Sep 26Sep 29Oct 1Oct 4Oct 7Oct 10Oct 13Oct 17
28°FSep 30Oct 4Oct 8Oct 11Oct 13Oct 16Oct 19Oct 22Oct 27
24°FOct 8Oct 13Oct 16Oct 19Oct 22Oct 25Oct 29Nov 1Nov 6
20°FOct 17Oct 23Oct 27Oct 30Nov 1Nov 4Nov 8Nov 11Nov 17
16°FOct 28Nov 1Nov 3Nov 6Nov 9Nov 12Nov 16Nov 20Nov 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°F151145140137134130126121115
32°F171165160157153149145140134
28°F193186181177172168163159153
24°F214207201196193188184179171
20°F233224219214210206202197189
16°F250243236232228223218212205

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
7,417
Cooling degree days, base 65°F
751
Growing degree days, base 40°F
4,718
Growing degree days, base 45°F
3,658
Growing degree days, base 50°F
2,733
Growing degree days, base 55°F
1,939
Growing degree days, base 60°F
1,276

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,42300
February1,17201
March943012
April555269
May27423247
June67109493
July12291744
August21253698
September15669375
October541589
November94207
December1,31300

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 22.5 km from Dawson County. 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 USC00243581 (Glendive). Public domain.