Mountrail County climate

Mountrail County Frost Dates and Growing Season

NOAA 1991-2020 normals for Stanley 3 Nnw, 17.8 km from Mountrail County, elevation 2280 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Stanley 3 Nnw. 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 17 and the first fall freeze around September 23, a growing season of about 127 days.

Median at 36°F
last May 27, first September 15
Median at 32°F
last May 17, first September 23
Median at 28°F
last May 8, first September 30

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 9Jun 3Jun 1May 29May 27May 24May 21May 18May 15
32°FMay 29May 25May 22May 19May 17May 14May 12May 10May 7
28°FMay 19May 15May 13May 10May 8May 6May 3May 1Apr 26
24°FMay 11May 7May 4May 2Apr 30Apr 27Apr 23Apr 18Apr 13
20°FMay 2Apr 27Apr 23Apr 20Apr 17Apr 15Apr 12Apr 9Apr 4
16°FApr 23Apr 18Apr 15Apr 12Apr 9Apr 6Apr 3Apr 1Mar 25

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 2Sep 7Sep 10Sep 13Sep 15Sep 17Sep 19Sep 22Sep 25
32°FSep 12Sep 16Sep 19Sep 21Sep 23Sep 25Sep 27Sep 30Oct 3
28°FSep 19Sep 22Sep 25Sep 27Sep 30Oct 3Oct 6Oct 10Oct 14
24°FSep 26Oct 1Oct 4Oct 7Oct 11Oct 13Oct 17Oct 20Oct 25
20°FOct 4Oct 11Oct 15Oct 17Oct 20Oct 23Oct 26Oct 29Nov 3
16°FOct 13Oct 19Oct 23Oct 26Oct 29Oct 31Nov 3Nov 6Nov 12

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°F1261201161121091061029893
32°F143137134130127124120117111
28°F163156152148145141137133126
24°F184178173169164160156151145
20°F204197192189184181176171164
16°F222215210206202198194189182

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
9,810
Cooling degree days, base 65°F
272
Growing degree days, base 40°F
3,403
Growing degree days, base 45°F
2,529
Growing degree days, base 50°F
1,768
Growing degree days, base 55°F
1,128
Growing degree days, base 60°F
622

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,75600
February1,48400
March1,26801
April783019
May4325134
June15435338
July52108521
August72103498
September29521221
October741135
November1,18401
December1,59000

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 17.8 km from Mountrail 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 USC00328276 (Stanley 3 Nnw). Public domain.