Steele County climate

Steele County Frost Dates and Growing Season

NOAA 1991-2020 normals for Owatonna, 8.4 km from Steele County, elevation 1140 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Owatonna. 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 5 and the first fall freeze around October 6, a growing season of about 154 days.

Median at 36°F
last May 14, first September 29
Median at 32°F
last May 5, first October 6
Median at 28°F
last April 25, first October 18

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 28May 23May 19May 16May 14May 10May 8May 5Apr 30
32°FMay 20May 14May 10May 8May 5May 2Apr 30Apr 25Apr 20
28°FMay 12May 6May 2Apr 30Apr 25Apr 22Apr 18Apr 16Apr 10
24°FMay 2Apr 26Apr 21Apr 18Apr 15Apr 11Apr 8Apr 5Apr 1
20°FApr 22Apr 16Apr 11Apr 7Apr 5Apr 2Mar 31Mar 26Mar 20
16°FApr 14Apr 7Apr 3Apr 1Mar 28Mar 24Mar 21Mar 17Mar 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 15Sep 20Sep 23Sep 26Sep 29Oct 1Oct 4Oct 6Oct 11
32°FSep 23Sep 28Oct 1Oct 4Oct 6Oct 9Oct 12Oct 16Oct 21
28°FOct 2Oct 7Oct 12Oct 15Oct 18Oct 21Oct 24Oct 27Nov 1
24°FOct 14Oct 20Oct 23Oct 26Oct 29Nov 1Nov 3Nov 6Nov 11
20°FOct 26Oct 30Nov 1Nov 3Nov 6Nov 8Nov 12Nov 16Nov 20
16°FNov 1Nov 5Nov 8Nov 11Nov 14Nov 17Nov 20Nov 24Nov 30

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°F156150146142138134130125119
32°F173166162157154150146142136
28°F196188183178174170165160154
24°F216209205200196191186181174
20°F237228222218213210206198190
16°F254246240235231226221216209

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
7,956
Cooling degree days, base 65°F
640
Growing degree days, base 40°F
4,558
Growing degree days, base 45°F
3,548
Growing degree days, base 50°F
2,644
Growing degree days, base 55°F
1,854
Growing degree days, base 60°F
1,181

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,59200
February1,31600
March1,06409
April610262
May27835258
June50144545
July10222677
August22162604
September15467374
October5257105
November950010
December1,38600

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 8.4 km from Steele 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 USC00216287 (Owatonna). Public domain.