Chisago County climate

Chisago County Frost Dates and Growing Season

NOAA 1991-2020 normals for Wild Rvr SP, 12.6 km from Chisago County, elevation 840 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Wild Rvr SP. 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 19 and the first fall freeze around September 25, a growing season of about 128 days.

Median at 36°F
last June 1, first September 16
Median at 32°F
last May 19, first September 25
Median at 28°F
last May 6, first October 4

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 14Jun 8Jun 5Jun 3Jun 1May 29May 26May 21May 15
32°FJun 3May 29May 26May 22May 19May 16May 12May 7May 2
28°FMay 22May 18May 13May 10May 6May 3Apr 30Apr 27Apr 23
24°FMay 12May 7May 3Apr 30Apr 28Apr 25Apr 22Apr 19Apr 14
20°FMay 2Apr 28Apr 24Apr 20Apr 17Apr 14Apr 11Apr 7Apr 3
16°FApr 24Apr 18Apr 13Apr 10Apr 7Apr 4Apr 2Mar 30Mar 23

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 1Sep 5Sep 9Sep 13Sep 16Sep 19Sep 22Sep 25Sep 30
32°FSep 10Sep 15Sep 19Sep 22Sep 25Sep 28Oct 1Oct 4Oct 8
28°FSep 18Sep 24Sep 28Oct 1Oct 4Oct 7Oct 10Oct 14Oct 19
24°FOct 1Oct 5Oct 9Oct 13Oct 17Oct 19Oct 23Oct 27Nov 1
20°FOct 12Oct 17Oct 22Oct 25Oct 29Nov 1Nov 3Nov 6Nov 12
16°FOct 23Oct 29Nov 1Nov 3Nov 5Nov 8Nov 12Nov 16Nov 20

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°F1271211161121081031009488
32°F149141136132128124120114107
28°F172163158153148144139134126
24°F192184179174170165160155147
20°F212205199195191188183177169
16°F232225220215212208202197189

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
8,608
Cooling degree days, base 65°F
446
Growing degree days, base 40°F
4,054
Growing degree days, base 45°F
3,094
Growing degree days, base 50°F
2,244
Growing degree days, base 55°F
1,516
Growing degree days, base 60°F
906

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,67100
February1,38900
March1,11906
April672143
May31823216
June8484452
July22172615
August42121544
September21340299
October605364
November1,01405
December1,46000

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 12.6 km from Chisago 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 USC00218986 (Wild Rvr SP). Public domain.