Monroe climate

Monroe Frost Dates and Growing Season

NOAA 1991-2020 normals for Des Moines 17 E, 15.7 km from Monroe, elevation 921 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Des Moines 17 E. 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 21 and the first fall freeze around October 15, a growing season of about 174 days.

Median at 36°F
last May 2, first October 3
Median at 32°F
last April 21, first October 15
Median at 28°F
last April 10, first October 25

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 15May 10May 7May 4May 2Apr 30Apr 26Apr 22Apr 18
32°FMay 5May 1Apr 28Apr 24Apr 21Apr 18Apr 15Apr 11Apr 7
28°FApr 26Apr 20Apr 16Apr 13Apr 10Apr 8Apr 5Apr 2Mar 29
24°FApr 17Apr 10Apr 7Apr 4Apr 2Mar 31Mar 28Mar 23Mar 16
20°FApr 7Apr 2Mar 30Mar 26Mar 23Mar 20Mar 16Mar 11Mar 6
16°FMar 30Mar 23Mar 19Mar 16Mar 13Mar 10Mar 7Mar 3Feb 27

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 19Sep 24Sep 28Oct 1Oct 3Oct 6Oct 9Oct 12Oct 17
32°FSep 30Oct 5Oct 10Oct 13Oct 15Oct 18Oct 21Oct 24Oct 27
28°FOct 13Oct 17Oct 21Oct 23Oct 25Oct 28Oct 30Nov 1Nov 6
24°FOct 23Oct 27Oct 30Nov 1Nov 3Nov 5Nov 8Nov 12Nov 16
20°FNov 1Nov 3Nov 6Nov 8Nov 11Nov 15Nov 18Nov 22Nov 29
16°FNov 6Nov 10Nov 14Nov 17Nov 20Nov 24Nov 28Dec 2Dec 7

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°F173167162158154151147142136
32°F193187183178174170165161154
28°F215208204200196192188183177
24°F236229223219215211207202196
20°F258250245240235231226221214
16°F274267262257253248243237229

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
6,420
Cooling degree days, base 65°F
816
Growing degree days, base 40°F
5,291
Growing degree days, base 45°F
4,149
Growing degree days, base 50°F
3,131
Growing degree days, base 55°F
2,229
Growing degree days, base 60°F
1,456

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,35100
February1,09603
March824234
April4446125
May17548349
June16172606
July4272733
August9216673
September10888434
October41312155
November803019
December1,17801

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 15.7 km from Monroe. 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 USW00054902 (Des Moines 17 E). Public domain.