Morrison County climate

Morrison County Frost Dates and Growing Season

NOAA 1991-2020 normals for Little Falls 2NNE, 6 km from Morrison County, elevation 1120 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Little Falls 2NNE. 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 4 and the first fall freeze around October 5, a growing season of about 151 days.

Median at 36°F
last May 17, first September 26
Median at 32°F
last May 4, first October 5
Median at 28°F
last April 24, first October 16

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 3May 29May 25May 20May 17May 13May 10May 6May 2
32°FMay 22May 14May 10May 7May 4May 1Apr 29Apr 26Apr 21
28°FMay 7May 2Apr 30Apr 27Apr 24Apr 22Apr 19Apr 15Apr 11
24°FApr 28Apr 23Apr 21Apr 18Apr 15Apr 13Apr 9Apr 6Apr 2
20°FApr 21Apr 17Apr 13Apr 10Apr 7Apr 4Apr 2Mar 30Mar 23
16°FApr 15Apr 9Apr 6Apr 3Mar 31Mar 29Mar 25Mar 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 11Sep 16Sep 20Sep 23Sep 26Sep 29Oct 1Oct 4Oct 9
32°FSep 22Sep 27Sep 30Oct 3Oct 5Oct 8Oct 11Oct 14Oct 19
28°FOct 1Oct 6Oct 10Oct 13Oct 16Oct 19Oct 23Oct 26Oct 31
24°FOct 13Oct 19Oct 23Oct 26Oct 29Nov 1Nov 2Nov 5Nov 10
20°FOct 23Oct 29Nov 1Nov 3Nov 5Nov 7Nov 9Nov 13Nov 17
16°FNov 1Nov 4Nov 6Nov 9Nov 11Nov 14Nov 16Nov 19Nov 23

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°F149142138133130125121114107
32°F170164159155151148143137131
28°F194187181178173169166161153
24°F212206201197194190186181174
20°F228222217214210207203198192
16°F246239234229226222218213207

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
7,950
Cooling degree days, base 65°F
657
Growing degree days, base 40°F
4,593
Growing degree days, base 45°F
3,575
Growing degree days, base 50°F
2,666
Growing degree days, base 55°F
1,871
Growing degree days, base 60°F
1,193

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,59000
February1,31600
March1,042011
April592163
May24734277
June55134530
July14245696
August23180622
September14658369
October528695
November97606
December1,42100

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 6 km from Morrison County. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00214793 (Little Falls 2NNE). Public domain.