Custer County climate

Custer County Frost Dates and Growing Season

NOAA 1991-2020 normals for Westcliffe, 9 km from Custer County, elevation 7873 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Westcliffe. 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 June 11 and the first fall freeze around September 9, a growing season of about 89 days.

Median at 32°F
last June 11, first September 9
Median at 28°F
last May 28, first September 20

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°F–––––––––
32°FJun 28Jun 23Jun 18Jun 14Jun 11Jun 7Jun 4Jun 2May 29
28°FJun 13Jun 7Jun 3May 31May 28May 24May 22May 19May 16
24°FMay 30May 23May 19May 16May 14May 11May 9May 6May 3
20°FMay 15May 10May 8May 6May 3May 1Apr 28Apr 25Apr 20
16°FMay 7May 3Apr 30Apr 26Apr 24Apr 20Apr 18Apr 14Apr 8

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°F–––––––––
32°FAug 28Sep 1Sep 4Sep 6Sep 9Sep 11Sep 14Sep 18Sep 23
28°FSep 6Sep 10Sep 13Sep 17Sep 20Sep 23Sep 26Sep 29Oct 2
24°FSep 16Sep 20Sep 24Sep 26Sep 29Oct 1Oct 3Oct 6Oct 10
20°FSep 24Sep 29Oct 1Oct 3Oct 6Oct 8Oct 11Oct 14Oct 19
16°FSep 30Oct 4Oct 7Oct 11Oct 13Oct 16Oct 19Oct 22Oct 28

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°F827468646054494235
32°F10810297938985807668
28°F13112512111711410910610194
24°F152147143139135132127122114
20°F173167162159155151148144138
16°F191185180176172167162158153

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
8,095
Cooling degree days, base 65°F
27
Growing degree days, base 40°F
3,032
Growing degree days, base 45°F
2,068
Growing degree days, base 50°F
1,279
Growing degree days, base 55°F
657
Growing degree days, base 60°F
218

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,27300
February1,06700
March94201
April719011
May479076
June1958266
July8313395
August1285343
September3101163
October660022
November96602
December1,27400

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 9 km from Custer 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 USC00058931 (Westcliffe). Public domain.