Belfield climate

Belfield Frost Dates and Growing Season

NOAA 1991-2020 normals for Medora 7 E, 13.5 km from Belfield, elevation 2771 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Medora 7 E. 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 9 and the first fall freeze around September 30, a growing season of about 142 days.

Median at 36°F
last May 19, first September 22
Median at 32°F
last May 9, first September 30
Median at 28°F
last April 30, first October 9

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 2May 29May 25May 22May 19May 17May 15May 12May 9
32°FMay 21May 17May 14May 11May 9May 7May 5May 3Apr 30
28°FMay 11May 6May 4May 1Apr 30Apr 27Apr 24Apr 20Apr 17
24°FMay 2Apr 29Apr 25Apr 22Apr 19Apr 16Apr 13Apr 10Apr 7
20°FApr 24Apr 19Apr 16Apr 13Apr 10Apr 8Apr 5Apr 2Mar 26
16°FApr 16Apr 11Apr 7Apr 4Apr 1Mar 29Mar 24Mar 19Mar 12

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 9Sep 13Sep 16Sep 20Sep 22Sep 25Sep 27Sep 29Oct 3
32°FSep 15Sep 21Sep 25Sep 27Sep 30Oct 2Oct 5Oct 9Oct 13
28°FSep 24Sep 29Oct 2Oct 5Oct 9Oct 12Oct 15Oct 19Oct 23
24°FOct 2Oct 8Oct 12Oct 15Oct 18Oct 21Oct 24Oct 27Nov 1
20°FOct 10Oct 17Oct 21Oct 25Oct 27Oct 30Nov 2Nov 6Nov 11
16°FOct 20Oct 26Oct 29Nov 1Nov 3Nov 6Nov 9Nov 14Nov 19

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°F140134130126123119115111104
32°F159153149146142138134129123
28°F180173168165161157153148142
24°F201194189184179175171166160
20°F220212206202199195190185178
16°F241231225221216211207202193

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
8,313
Cooling degree days, base 65°F
439
Growing degree days, base 40°F
3,960
Growing degree days, base 45°F
2,996
Growing degree days, base 50°F
2,157
Growing degree days, base 55°F
1,447
Growing degree days, base 60°F
869

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,46600
February1,25600
March1,06006
April698029
May3748162
June11547387
July20175620
August39164590
September22343298
October644261
November1,03404
December1,38500

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 13.5 km from Belfield. 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 USW00094080 (Medora 7 E). Public domain.