Manson climate

Manson Frost Dates and Growing Season

NOAA 1991-2020 normals for Rockwell City, 16.6 km from Manson, elevation 1214 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rockwell City. 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 26 and the first fall freeze around October 10, a growing season of about 167 days.

Median at 36°F
last May 4, first October 1
Median at 32°F
last April 26, first October 10
Median at 28°F
last April 16, first October 21

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 11May 8May 6May 4May 2Apr 30Apr 27Apr 23
32°FMay 6May 3May 1Apr 29Apr 26Apr 23Apr 21Apr 17Apr 11
28°FApr 29Apr 25Apr 22Apr 19Apr 16Apr 13Apr 10Apr 7Apr 2
24°FApr 22Apr 17Apr 14Apr 10Apr 7Apr 5Apr 2Mar 30Mar 23
20°FApr 15Apr 9Apr 5Apr 2Mar 31Mar 29Mar 24Mar 19Mar 14
16°FApr 6Apr 1Mar 29Mar 25Mar 21Mar 17Mar 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 18Sep 22Sep 26Sep 28Oct 1Oct 3Oct 5Oct 9Oct 13
32°FSep 27Oct 1Oct 4Oct 7Oct 10Oct 13Oct 16Oct 19Oct 24
28°FOct 6Oct 11Oct 15Oct 18Oct 21Oct 24Oct 27Oct 31Nov 4
24°FOct 18Oct 23Oct 26Oct 29Nov 1Nov 2Nov 5Nov 9Nov 13
20°FOct 25Oct 31Nov 2Nov 5Nov 8Nov 10Nov 13Nov 18Nov 23
16°FNov 1Nov 5Nov 9Nov 12Nov 16Nov 19Nov 22Nov 26Dec 1

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°F166160156151148145142138132
32°F186180175171167164160155148
28°F206199195191188184179175168
24°F227218213209205202199194186
20°F243237231226222217213208202
16°F259252247243239233229224217

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
7,187
Cooling degree days, base 65°F
733
Growing degree days, base 40°F
4,926
Growing degree days, base 45°F
3,851
Growing degree days, base 50°F
2,888
Growing degree days, base 55°F
2,043
Growing degree days, base 60°F
1,322

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,47400
February1,20801
March938017
April532485
May21843309
June30166587
July6250710
August15188639
September13173398
October4648129
November882014
December1,29000

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 16.6 km from Manson. 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 USC00137161 (Rockwell City). Public domain.