Ranchettes climate

Ranchettes Frost Dates and Growing Season

NOAA 1991-2020 normals for Cheyenne, 7.6 km from Ranchettes, elevation 6128 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cheyenne. 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 12 and the first fall freeze around October 1, a growing season of about 141 days.

Median at 36°F
last May 24, first September 24
Median at 32°F
last May 12, first October 1
Median at 28°F
last May 2, first October 11

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 8Jun 3May 31May 27May 24May 22May 19May 16May 12
32°FMay 26May 21May 18May 15May 12May 10May 8May 5May 1
28°FMay 14May 10May 6May 4May 2Apr 30Apr 27Apr 23Apr 19
24°FMay 5May 2Apr 29Apr 26Apr 22Apr 18Apr 14Apr 9Apr 4
20°FApr 29Apr 23Apr 17Apr 13Apr 9Apr 6Apr 2Mar 29Mar 22
16°FApr 20Apr 11Apr 6Apr 1Mar 29Mar 24Mar 20Mar 12Mar 5

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 10Sep 16Sep 19Sep 22Sep 24Sep 26Sep 29Oct 1Oct 5
32°FSep 18Sep 24Sep 27Sep 30Oct 1Oct 4Oct 7Oct 10Oct 14
28°FSep 28Oct 1Oct 5Oct 9Oct 11Oct 13Oct 16Oct 19Oct 24
24°FOct 5Oct 11Oct 14Oct 17Oct 20Oct 23Oct 26Oct 29Nov 3
20°FOct 14Oct 18Oct 22Oct 26Oct 29Nov 1Nov 4Nov 8Nov 12
16°FOct 19Oct 24Oct 30Nov 1Nov 5Nov 8Nov 11Nov 16Nov 22

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°F138133129125121117113109102
32°F158152148145141138134129122
28°F180173168165161157153149141
24°F201195190186182176172167160
20°F224216210205200195190185176
16°F248239231224219213207201192

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
6,959
Cooling degree days, base 65°F
399
Growing degree days, base 40°F
4,108
Growing degree days, base 45°F
3,049
Growing degree days, base 50°F
2,163
Growing degree days, base 55°F
1,432
Growing degree days, base 60°F
843

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,11001
February99401
March86509
April666029
May3984151
June11556396
July17175623
August33130563
September19632309
October574172
November867010
December1,12501

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 7.6 km from Ranchettes. 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 USW00024018 (Cheyenne). Public domain.