Conrad climate

Conrad Frost Dates and Growing Season

NOAA 1991-2020 normals for Marshalltown Muni AP, 13 km from Conrad, elevation 974 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Marshalltown Muni AP. 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 6, a growing season of about 159 days.

Median at 36°F
last May 7, first September 26
Median at 32°F
last April 30, first October 6
Median at 28°F
last April 19, 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°FMay 20May 16May 12May 10May 7May 5May 2Apr 30Apr 26
32°FMay 12May 7May 4May 2Apr 30Apr 27Apr 24Apr 21Apr 15
28°FMay 3Apr 30Apr 26Apr 23Apr 19Apr 16Apr 13Apr 10Apr 5
24°FApr 25Apr 20Apr 15Apr 11Apr 9Apr 6Apr 3Apr 1Mar 27
20°FApr 16Apr 9Apr 6Apr 3Mar 31Mar 29Mar 26Mar 20Mar 14
16°FApr 7Apr 1Mar 29Mar 25Mar 21Mar 18Mar 14Mar 10Mar 5

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 14Sep 18Sep 21Sep 24Sep 26Sep 29Oct 2Oct 5Oct 9
32°FSep 22Sep 27Sep 30Oct 3Oct 6Oct 9Oct 12Oct 15Oct 19
28°FSep 30Oct 6Oct 10Oct 14Oct 16Oct 19Oct 21Oct 24Oct 28
24°FOct 14Oct 18Oct 21Oct 23Oct 26Oct 29Oct 31Nov 3Nov 8
20°FOct 23Oct 28Oct 31Nov 1Nov 4Nov 7Nov 10Nov 13Nov 18
16°FOct 31Nov 3Nov 6Nov 10Nov 13Nov 16Nov 20Nov 24Nov 30

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°F158153149145141137134130124
32°F178171167163159154150146140
28°F198192188183179174170166159
24°F219211207203199195191186180
20°F240232228223219214210204197
16°F259252246241237232229223214

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
6,996
Cooling degree days, base 65°F
727
Growing degree days, base 40°F
4,957
Growing degree days, base 45°F
3,871
Growing degree days, base 50°F
2,900
Growing degree days, base 55°F
2,049
Growing degree days, base 60°F
1,318

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,42900
February1,17001
March908122
April506493
May20549324
June26169592
July7244702
August17180628
September13571393
October46710130
November864015
December1,26001

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 13 km from Conrad. 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 USW00094988 (Marshalltown Muni AP). Public domain.