Mower County climate

Mower County Frost Dates and Growing Season

NOAA 1991-2020 normals for Grand Meadow, 15.5 km from Mower County, elevation 1350 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Grand Meadow. 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 6 and the first fall freeze around October 1, a growing season of about 146 days.

Median at 36°F
last May 14, first September 22
Median at 32°F
last May 6, first October 1
Median at 28°F
last April 27, first October 9

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 26May 22May 19May 17May 14May 12May 10May 7May 3
32°FMay 18May 14May 11May 9May 6May 4May 1Apr 29Apr 23
28°FMay 10May 5May 2Apr 30Apr 27Apr 24Apr 21Apr 17Apr 11
24°FApr 30Apr 26Apr 23Apr 18Apr 15Apr 12Apr 9Apr 6Apr 2
20°FApr 22Apr 16Apr 12Apr 9Apr 6Apr 4Apr 2Mar 30Mar 23
16°FApr 13Apr 7Apr 4Apr 2Mar 31Mar 27Mar 23Mar 20Mar 15

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 9Sep 14Sep 18Sep 20Sep 22Sep 25Sep 28Oct 1Oct 5
32°FSep 17Sep 21Sep 25Sep 28Oct 1Oct 3Oct 6Oct 9Oct 13
28°FSep 25Sep 30Oct 3Oct 7Oct 9Oct 13Oct 15Oct 18Oct 23
24°FOct 5Oct 10Oct 15Oct 18Oct 21Oct 23Oct 26Oct 29Nov 3
20°FOct 18Oct 23Oct 25Oct 28Oct 31Nov 2Nov 5Nov 9Nov 14
16°FOct 29Nov 1Nov 4Nov 7Nov 10Nov 13Nov 16Nov 20Nov 25

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°F149143138135131127124120113
32°F165159154150146143139135128
28°F186179173169165161156151143
24°F207199194190186181177171165
20°F228220215211208203199194187
16°F247239234229225221217212206

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
8,407
Cooling degree days, base 65°F
408
Growing degree days, base 40°F
4,053
Growing degree days, base 45°F
3,083
Growing degree days, base 50°F
2,226
Growing degree days, base 55°F
1,487
Growing degree days, base 60°F
871

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,62000
February1,35100
March1,11607
April670141
May32522209
June6997479
July24147587
August4799518
September20538303
October585476
November99006
December1,40600

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 15.5 km from Mower 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 USC00213290 (Grand Meadow). Public domain.