Mount Carroll climate

Mount Carroll Frost Dates and Growing Season

NOAA 1991-2020 normals for Mt Carroll, 0.6 km from Mount Carroll, elevation 640 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mt Carroll. 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 2 and the first fall freeze around October 7, a growing season of about 154 days.

Median at 36°F
last May 14, first September 27
Median at 32°F
last May 2, first October 7
Median at 28°F
last April 23, 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 28May 24May 20May 17May 14May 10May 7May 3Apr 30
32°FMay 18May 13May 9May 6May 2Apr 30Apr 27Apr 23Apr 18
28°FMay 9May 3Apr 30Apr 26Apr 23Apr 20Apr 17Apr 13Apr 9
24°FApr 28Apr 23Apr 19Apr 16Apr 13Apr 9Apr 6Apr 3Mar 31
20°FApr 17Apr 12Apr 7Apr 4Apr 2Mar 31Mar 26Mar 21Mar 15
16°FApr 4Apr 1Mar 29Mar 24Mar 20Mar 16Mar 13Mar 9Mar 4

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

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°F154147143139135131127122116
32°F171166162158154151147142136
28°F194187182178174170166162154
24°F217210205201197192188182176
20°F243234229224219215211205198
16°F263257251246242238233228220

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
6,733
Cooling degree days, base 65°F
746
Growing degree days, base 40°F
4,994
Growing degree days, base 45°F
3,895
Growing degree days, base 50°F
2,917
Growing degree days, base 55°F
2,066
Growing degree days, base 60°F
1,338

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,37000
February1,12601
March882121
April509592
May21150321
June35165581
July7244702
August16192642
September13077403
October44110135
November812018
December1,19502

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 0.6 km from Mount Carroll. 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 USC00115901 (Mt Carroll). Public domain.