Penrose climate

Penrose Frost Dates and Growing Season

NOAA 1991-2020 normals for Canon City, 18.1 km from Penrose, elevation 5378 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Canon City. 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 4 and the first fall freeze around October 7, a growing season of about 153 days.

Median at 36°F
last May 16, first September 28
Median at 32°F
last May 4, first October 7
Median at 28°F
last April 26, first October 17

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 1May 26May 22May 19May 16May 13May 10May 7May 3
32°FMay 18May 13May 9May 6May 4May 2Apr 30Apr 28Apr 24
28°FMay 7May 4May 1Apr 29Apr 26Apr 23Apr 20Apr 17Apr 13
24°FApr 30Apr 24Apr 21Apr 18Apr 15Apr 12Apr 9Apr 5Mar 31
20°FApr 19Apr 14Apr 10Apr 6Apr 2Mar 31Mar 27Mar 22Mar 15
16°FApr 10Apr 3Mar 31Mar 25Mar 22Mar 16Mar 12Mar 7Mar 1

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 14Sep 20Sep 23Sep 26Sep 28Sep 30Oct 2Oct 5Oct 9
32°FSep 25Sep 29Oct 2Oct 4Oct 7Oct 10Oct 12Oct 15Oct 19
28°FOct 3Oct 7Oct 11Oct 14Oct 17Oct 19Oct 22Oct 25Oct 29
24°FOct 13Oct 17Oct 21Oct 24Oct 27Oct 30Nov 1Nov 4Nov 9
20°FOct 19Oct 24Oct 29Nov 1Nov 4Nov 7Nov 10Nov 14Nov 18
16°FOct 29Nov 2Nov 7Nov 11Nov 14Nov 17Nov 19Nov 23Nov 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°F149144140137134131126122114
32°F169163159156153150146141136
28°F189184179175171167163158152
24°F211205200195192188183179172
20°F236227222216212208204199191
16°F261251245239234228224217209

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
5,440
Cooling degree days, base 65°F
751
Growing degree days, base 40°F
5,351
Growing degree days, base 45°F
4,088
Growing degree days, base 50°F
3,011
Growing degree days, base 55°F
2,101
Growing degree days, base 60°F
1,349

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January96403
February83906
March704029
April489188
May23522279
June38140552
July3281742
August10225680
September10077434
October3964159
November698033
December96605

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 18.1 km from Penrose. 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 USC00051294 (Canon City). Public domain.