Ottawa County climate

Ottawa County Frost Dates and Growing Season

NOAA 1991-2020 normals for Minneapolis, 4.8 km from Ottawa County, elevation 1306 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Minneapolis. 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 April 20 and the first fall freeze around October 19, a growing season of about 181 days.

Median at 36°F
last April 29, first October 9
Median at 32°F
last April 20, first October 19
Median at 28°F
last April 10, first October 29

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 12May 7May 3May 1Apr 29Apr 26Apr 23Apr 20Apr 15
32°FMay 3Apr 30Apr 26Apr 22Apr 20Apr 16Apr 14Apr 10Apr 6
28°FApr 24Apr 20Apr 16Apr 12Apr 10Apr 7Apr 4Apr 1Mar 26
24°FApr 15Apr 9Apr 6Apr 4Apr 1Mar 29Mar 25Mar 21Mar 14
20°FApr 7Apr 1Mar 29Mar 25Mar 21Mar 16Mar 13Mar 9Mar 4
16°FMar 30Mar 22Mar 17Mar 13Mar 10Mar 6Mar 3Feb 28Feb 21

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 25Sep 30Oct 2Oct 6Oct 9Oct 12Oct 15Oct 18Oct 22
32°FOct 3Oct 10Oct 13Oct 16Oct 19Oct 21Oct 24Oct 28Nov 1
28°FOct 14Oct 19Oct 22Oct 26Oct 29Nov 1Nov 3Nov 5Nov 10
24°FOct 23Oct 28Nov 1Nov 3Nov 6Nov 9Nov 12Nov 16Nov 21
20°FOct 31Nov 4Nov 8Nov 12Nov 15Nov 18Nov 22Nov 26Dec 2
16°FNov 8Nov 16Nov 19Nov 23Nov 27Dec 1Dec 4Dec 8Dec 15

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°F181175170166163160155151144
32°F201194189185181177173167160
28°F223215210206202197193188181
24°F245235230225221216211206198
20°F264255250245240235230224214
16°F284276270265260255250244235

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
5,153
Cooling degree days, base 65°F
1,561
Growing degree days, base 40°F
6,601
Growing degree days, base 45°F
5,331
Growing degree days, base 50°F
4,195
Growing degree days, base 55°F
3,190
Growing degree days, base 60°F
2,311

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,10701
February88109
March659261
April34916187
May114105460
June7320763
July0488953
August2408871
September50191592
October29430252
November667144
December1,02402

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 4.8 km from Ottawa 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 USC00145363 (Minneapolis). Public domain.