Carroll County climate

Carroll County Frost Dates and Growing Season

NOAA 1991-2020 normals for Harrison Boone CO AP, 35.2 km from Carroll County, elevation 1374 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Harrison Boone CO 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 3 and the first fall freeze around October 30, a growing season of about 210 days.

Median at 36°F
last April 15, first October 21
Median at 32°F
last April 3, first October 30
Median at 28°F
last March 24, first November 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 2Apr 27Apr 22Apr 18Apr 15Apr 11Apr 8Apr 4Mar 30
32°FApr 21Apr 14Apr 10Apr 6Apr 3Mar 31Mar 28Mar 24Mar 17
28°FApr 9Apr 4Mar 31Mar 27Mar 24Mar 20Mar 16Mar 11Mar 4
24°FMar 31Mar 24Mar 19Mar 15Mar 11Mar 7Mar 4Feb 28Feb 22
20°FMar 17Mar 12Mar 7Mar 3Mar 1Feb 25Feb 21Feb 15Feb 7
16°FMar 11Mar 4Feb 28Feb 24Feb 19Feb 14Feb 8Feb 3Jan 26

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°FOct 7Oct 11Oct 15Oct 18Oct 21Oct 23Oct 26Oct 29Nov 2
32°FOct 16Oct 21Oct 25Oct 27Oct 30Nov 1Nov 4Nov 8Nov 14
28°FOct 27Nov 1Nov 4Nov 7Nov 10Nov 14Nov 18Nov 24Nov 30
24°FNov 4Nov 9Nov 14Nov 18Nov 22Nov 27Nov 30Dec 4Dec 11
20°FNov 13Nov 20Nov 25Nov 29Dec 3Dec 7Dec 13Dec 19Dec 26
16°FNov 24Nov 30Dec 6Dec 11Dec 18Dec 22Dec 28Jan 2Jan 12

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°F209201195191186182177172166
32°F231224218214210205201195187
28°F256247242237232228222217208
24°F282272265259254249243237229
20°F308298290283277272266259250
16°F332321313306300295288279270

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
3,883
Cooling degree days, base 65°F
1,475
Growing degree days, base 40°F
7,218
Growing degree days, base 45°F
5,768
Growing degree days, base 50°F
4,463
Growing degree days, base 55°F
3,310
Growing degree days, base 60°F
2,312

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January867021
February676135
March4978119
April23231277
May75112504
June4286732
July0419883
August1391855
September34182599
October21440312
November5005100
December785027

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 35.2 km from Carroll County. 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 USW00013971 (Harrison Boone CO AP). Public domain.