Mapleton climate

Mapleton Frost Dates and Growing Season

NOAA 1991-2020 normals for Mapleton No.2, 0.9 km from Mapleton, elevation 1200 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mapleton No.2. 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 3 and the first fall freeze around October 1, a growing season of about 151 days.

Median at 36°F
last May 11, first September 24
Median at 32°F
last May 3, first October 1
Median at 28°F
last April 24, first October 12

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

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 15Sep 19Sep 22Sep 24Sep 27Sep 30Oct 3Oct 6
32°FSep 19Sep 23Sep 27Sep 29Oct 1Oct 5Oct 7Oct 11Oct 17
28°FSep 27Oct 1Oct 5Oct 9Oct 12Oct 16Oct 19Oct 23Oct 26
24°FOct 7Oct 14Oct 18Oct 21Oct 23Oct 26Oct 29Nov 1Nov 4
20°FOct 19Oct 24Oct 28Oct 31Nov 1Nov 3Nov 6Nov 10Nov 15
16°FOct 28Nov 1Nov 3Nov 6Nov 8Nov 12Nov 15Nov 20Nov 26

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°F154147143140137133129125119
32°F170164159155151148144140134
28°F190183178175170167163158151
24°F210203199195191187182177170
20°F230222217212209205201196189
16°F251242236232227223218212206

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
7,195
Cooling degree days, base 65°F
738
Growing degree days, base 40°F
4,879
Growing degree days, base 45°F
3,809
Growing degree days, base 50°F
2,856
Growing degree days, base 55°F
2,021
Growing degree days, base 60°F
1,312

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,44700
February1,18001
March923019
April536486
May23043302
June33166583
July7258716
August22186629
September14672386
October4859122
November897013
December1,28900

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 0.9 km from Mapleton. 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 USC00135123 (Mapleton No.2). Public domain.