Colo climate

Colo Frost Dates and Growing Season

NOAA 1991-2020 normals for Colo, 0.3 km from Colo, elevation 1000 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Colo. 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 24 and the first fall freeze around October 12, a growing season of about 170 days.

Median at 36°F
last May 4, first October 1
Median at 32°F
last April 24, first October 12
Median at 28°F
last April 14, first October 23

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

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 19Sep 24Sep 27Sep 29Oct 1Oct 4Oct 8Oct 11Oct 16
32°FSep 28Oct 1Oct 5Oct 9Oct 12Oct 15Oct 18Oct 21Oct 26
28°FOct 9Oct 14Oct 17Oct 20Oct 23Oct 25Oct 28Oct 31Nov 4
24°FOct 20Oct 24Oct 27Oct 30Nov 1Nov 3Nov 6Nov 9Nov 15
20°FOct 27Nov 1Nov 3Nov 6Nov 9Nov 12Nov 16Nov 21Nov 27
16°FNov 4Nov 8Nov 12Nov 16Nov 19Nov 23Nov 27Dec 1Dec 5

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°F170163158155151148144139133
32°F190183178174170166162157150
28°F212205199195191187183178170
24°F231223219214210206202196188
20°F250243237232227223218213207
16°F268261256251246242237231223

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
7,020
Cooling degree days, base 65°F
780
Growing degree days, base 40°F
5,028
Growing degree days, base 45°F
3,944
Growing degree days, base 50°F
2,971
Growing degree days, base 55°F
2,118
Growing degree days, base 60°F
1,380

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,44600
February1,18601
March920119
April513694
May20745319
June29179600
July5257718
August12203655
September12680410
October45510135
November857020
December1,26601

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 0.3 km from Colo. 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 USC00131710 (Colo). Public domain.