Mankato climate

Mankato Frost Dates and Growing Season

NOAA 1991-2020 normals for Mankato, 0.6 km from Mankato, elevation 1750 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mankato. 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 30 and the first fall freeze around October 14, a growing season of about 165 days.

Median at 36°F
last May 8, first October 4
Median at 32°F
last April 30, first October 14
Median at 28°F
last April 20, first October 23

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 21May 17May 14May 11May 8May 5May 3Apr 30Apr 26
32°FMay 14May 9May 6May 3Apr 30Apr 28Apr 25Apr 21Apr 15
28°FMay 5May 1Apr 28Apr 23Apr 20Apr 16Apr 12Apr 8Apr 4
24°FApr 25Apr 20Apr 16Apr 11Apr 8Apr 5Apr 2Mar 31Mar 23
20°FApr 16Apr 9Apr 5Apr 2Mar 31Mar 28Mar 23Mar 19Mar 13
16°FApr 5Mar 31Mar 28Mar 24Mar 20Mar 16Mar 12Mar 7Mar 1

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 20Sep 25Sep 29Oct 1Oct 4Oct 6Oct 10Oct 13Oct 18
32°FSep 28Oct 2Oct 6Oct 11Oct 14Oct 17Oct 20Oct 22Oct 26
28°FOct 5Oct 13Oct 18Oct 21Oct 23Oct 25Oct 28Oct 31Nov 4
24°FOct 18Oct 23Oct 26Oct 30Nov 1Nov 3Nov 5Nov 8Nov 13
20°FOct 27Oct 31Nov 3Nov 5Nov 8Nov 10Nov 14Nov 18Nov 24
16°FNov 1Nov 6Nov 9Nov 13Nov 15Nov 19Nov 23Nov 28Dec 4

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°F167160155152148144140136130
32°F184179173169165161157151146
28°F205198193188184180174169163
24°F227219213209204200196191182
20°F246238232228224220215209201
16°F267259251246242237232226218

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
5,976
Cooling degree days, base 65°F
1,167
Growing degree days, base 40°F
5,767
Growing degree days, base 45°F
4,589
Growing degree days, base 50°F
3,531
Growing degree days, base 55°F
2,612
Growing degree days, base 60°F
1,826

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,22000
February98904
March780035
April4566118
May18855344
June22242670
July1410874
August6323782
September87117483
October36115192
November754028
December1,11301

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 0.6 km from Mankato. 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 USC00144982 (Mankato). Public domain.