Keewatin climate

Keewatin Frost Dates and Growing Season

NOAA 1991-2020 normals for Hibbing Chisholm Hibbing AP, 17.6 km from Keewatin, elevation 1352 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hibbing Chisholm Hibbing AP. 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 June 5 and the first fall freeze around September 8, a growing season of about 93 days.

Median at 32°F
last June 5, first September 8
Median at 28°F
last May 23, first September 21

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°F–––––––––
32°FJun 25Jun 17Jun 12Jun 8Jun 5Jun 2May 30May 27May 22
28°FJun 7Jun 1May 29May 26May 23May 20May 16May 12May 6
24°FMay 24May 19May 15May 11May 7May 4May 1Apr 29Apr 25
20°FMay 12May 7May 3Apr 30Apr 28Apr 25Apr 21Apr 18Apr 12
16°FApr 30Apr 26Apr 22Apr 19Apr 16Apr 13Apr 9Apr 6Apr 2

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°F–––––––––
32°FAug 23Aug 29Sep 2Sep 5Sep 8Sep 12Sep 15Sep 19Sep 23
28°FSep 4Sep 11Sep 15Sep 18Sep 21Sep 24Sep 27Oct 1Oct 5
24°FSep 16Sep 21Sep 25Sep 29Oct 1Oct 3Oct 6Oct 11Oct 17
20°FSep 28Oct 3Oct 7Oct 11Oct 15Oct 19Oct 22Oct 27Nov 1
16°FOct 12Oct 18Oct 22Oct 27Oct 31Nov 2Nov 4Nov 7Nov 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°F877972676156494436
32°F115108102979389847767
28°F14213413012412011511110597
24°F165158154149144140135130121
20°F192185179174169164159154147
16°F215209204199195191186181172

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
10,336
Cooling degree days, base 65°F
120
Growing degree days, base 40°F
2,875
Growing degree days, base 45°F
2,042
Growing degree days, base 50°F
1,336
Growing degree days, base 55°F
766
Growing degree days, base 60°F
357

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,82100
February1,52500
March1,27701
April836010
May483497
June20221276
July9851419
August14136361
September3699152
October767020
November1,18201
December1,63500

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 17.6 km from Keewatin. 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 USW00094931 (Hibbing Chisholm Hibbing AP). Public domain.