Stapleton climate

Stapleton Frost Dates and Growing Season

NOAA 1991-2020 normals for Stapleton 5W, 7.5 km from Stapleton, elevation 3022 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Stapleton 5W. 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 8 and the first fall freeze around October 3, a growing season of about 146 days.

Median at 36°F
last May 18, first September 25
Median at 32°F
last May 8, first October 3
Median at 28°F
last April 30, first October 12

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°FJun 2May 29May 25May 21May 18May 16May 13May 10May 5
32°FMay 24May 18May 14May 11May 8May 6May 3Apr 30Apr 26
28°FMay 12May 7May 4May 2Apr 30Apr 27Apr 23Apr 18Apr 14
24°FMay 3Apr 30Apr 27Apr 22Apr 18Apr 15Apr 12Apr 8Apr 3
20°FApr 25Apr 19Apr 15Apr 11Apr 8Apr 5Apr 1Mar 27Mar 21
16°FApr 16Apr 9Apr 5Apr 1Mar 29Mar 25Mar 21Mar 16Mar 9

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 11Sep 17Sep 20Sep 22Sep 25Sep 27Sep 30Oct 2Oct 6
32°FSep 20Sep 25Sep 28Oct 1Oct 3Oct 5Oct 8Oct 11Oct 15
28°FSep 28Oct 2Oct 6Oct 10Oct 12Oct 15Oct 17Oct 20Oct 24
24°FOct 6Oct 12Oct 16Oct 19Oct 21Oct 23Oct 26Oct 29Nov 3
20°FOct 15Oct 20Oct 23Oct 26Oct 29Nov 1Nov 4Nov 8Nov 13
16°FOct 23Oct 28Nov 1Nov 4Nov 6Nov 10Nov 14Nov 17Nov 23

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°F147140136133129126122117111
32°F163157153149146142139134127
28°F184177172168164161156152146
24°F205197193188185180176170163
20°F226218213207204199195190181
16°F247239232227222217213207201

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
6,792
Cooling degree days, base 65°F
692
Growing degree days, base 40°F
4,789
Growing degree days, base 45°F
3,692
Growing degree days, base 50°F
2,737
Growing degree days, base 55°F
1,921
Growing degree days, base 60°F
1,241

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,24600
February1,05501
March857017
April562169
May28026250
June53130528
July8262719
August18203649
September14767382
October5023109
November867013
December1,19500

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 7.5 km from Stapleton. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00258133 (Stapleton 5W). Public domain.