Sheridan climate

Sheridan Frost Dates and Growing Season

NOAA 1991-2020 normals for Sheridan CO AP, 3.2 km from Sheridan, elevation 3945 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Sheridan 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 May 21 and the first fall freeze around September 23, a growing season of about 123 days.

Median at 36°F
last June 4, first September 13
Median at 32°F
last May 21, first September 23
Median at 28°F
last May 7, first October 3

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 19Jun 14Jun 11Jun 8Jun 4Jun 1May 29May 25May 21
32°FJun 6May 31May 27May 24May 21May 18May 15May 12May 7
28°FMay 22May 16May 13May 9May 7May 4May 2Apr 29Apr 25
24°FMay 10May 4May 1Apr 28Apr 25Apr 22Apr 18Apr 15Apr 10
20°FApr 30Apr 24Apr 19Apr 16Apr 13Apr 10Apr 6Apr 3Mar 29
16°FApr 20Apr 15Apr 10Apr 5Apr 2Mar 31Mar 26Mar 18Mar 11

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°FAug 30Sep 3Sep 7Sep 10Sep 13Sep 15Sep 18Sep 21Sep 25
32°FSep 9Sep 16Sep 18Sep 21Sep 23Sep 26Sep 28Oct 1Oct 6
28°FSep 20Sep 24Sep 28Oct 1Oct 3Oct 6Oct 9Oct 13Oct 17
24°FSep 28Oct 2Oct 6Oct 10Oct 13Oct 16Oct 19Oct 22Oct 26
20°FOct 5Oct 11Oct 16Oct 19Oct 22Oct 25Oct 28Nov 1Nov 6
16°FOct 15Oct 20Oct 24Oct 28Oct 30Nov 2Nov 6Nov 10Nov 15

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°F1181111061019893908578
32°F143136131127123120115110102
28°F166159155151147143139134126
24°F191183178174169165160156148
20°F213206201196191186181175166
16°F235227221215211206201195187

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
7,542
Cooling degree days, base 65°F
441
Growing degree days, base 40°F
4,019
Growing degree days, base 45°F
2,995
Growing degree days, base 50°F
2,136
Growing degree days, base 55°F
1,430
Growing degree days, base 60°F
864

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,27100
February1,09001
March90808
April654030
May3944141
June13843361
July22197640
August37162591
September21234294
October608263
November95107
December1,25700

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 3.2 km from Sheridan. 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 USW00024029 (Sheridan CO AP). Public domain.