Mapleton climate

Mapleton Frost Dates and Growing Season

NOAA 1991-2020 normals for Casselton Agronomy Farm, 13.7 km from Mapleton, elevation 935 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Casselton Agronomy Farm. 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 9 and the first fall freeze around October 1, a growing season of about 143 days.

Median at 36°F
last May 18, first September 22
Median at 32°F
last May 9, first October 1
Median at 28°F
last April 29, first October 10

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 29May 25May 22May 20May 18May 15May 12May 9May 4
32°FMay 21May 17May 14May 11May 9May 5May 3Apr 30Apr 25
28°FMay 13May 9May 4May 1Apr 29Apr 26Apr 22Apr 18Apr 12
24°FMay 3Apr 28Apr 25Apr 21Apr 18Apr 14Apr 11Apr 8Apr 5
20°FApr 24Apr 18Apr 13Apr 11Apr 8Apr 6Apr 4Apr 1Mar 27
16°FApr 16Apr 11Apr 7Apr 5Apr 3Apr 1Mar 29Mar 24Mar 17

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 10Sep 14Sep 17Sep 19Sep 22Sep 24Sep 26Sep 29Oct 3
32°FSep 17Sep 22Sep 26Sep 29Oct 1Oct 3Oct 6Oct 9Oct 15
28°FSep 26Oct 1Oct 4Oct 7Oct 10Oct 14Oct 17Oct 21Oct 24
24°FOct 4Oct 10Oct 13Oct 18Oct 21Oct 25Oct 28Oct 31Nov 3
20°FOct 14Oct 22Oct 25Oct 28Oct 31Nov 2Nov 5Nov 8Nov 13
16°FOct 26Oct 31Nov 2Nov 4Nov 7Nov 10Nov 13Nov 16Nov 22

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°F144137133129126123119115108
32°F163156151147143140137133126
28°F183177171167163159155150143
24°F204197192187183179175168161
20°F221214210206203199194187181
16°F236229225221217214210205198

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
9,114
Cooling degree days, base 65°F
449
Growing degree days, base 40°F
4,016
Growing degree days, base 45°F
3,076
Growing degree days, base 50°F
2,246
Growing degree days, base 55°F
1,520
Growing degree days, base 60°F
915

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,77500
February1,48800
March1,21501
April699034
May31821220
June6998479
July21167611
August39127553
September21835287
October632359
November1,08801
December1,55300

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 13.7 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 USC00321408 (Casselton Agronomy Farm). Public domain.