High Rolls climate

High Rolls Frost Dates and Growing Season

NOAA 1991-2020 normals for Mtn Park, 1.2 km from High Rolls, elevation 6804 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mtn Park. 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 April 30 and the first fall freeze around October 21, a growing season of about 173 days.

Median at 36°F
last May 11, first October 12
Median at 32°F
last April 30, first October 21
Median at 28°F
last April 20, first October 30

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°FMay 30May 22May 17May 14May 11May 7May 4Apr 30Apr 27
32°FMay 15May 10May 6May 3Apr 30Apr 27Apr 24Apr 21Apr 16
28°FMay 5Apr 30Apr 26Apr 23Apr 20Apr 16Apr 11Apr 6Apr 1
24°FApr 22Apr 16Apr 9Apr 5Apr 2Mar 30Mar 24Mar 17Mar 8
20°FApr 4Mar 28Mar 22Mar 16Mar 9Mar 5Feb 28Feb 20Feb 11
16°FMar 15Mar 6Mar 1Feb 22Feb 16Feb 10Feb 3Jan 28Jan 14

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°FOct 2Oct 5Oct 8Oct 10Oct 12Oct 15Oct 18Oct 21Oct 24
32°FOct 9Oct 13Oct 16Oct 19Oct 21Oct 23Oct 26Oct 30Nov 4
28°FOct 14Oct 20Oct 23Oct 26Oct 30Nov 1Nov 5Nov 9Nov 14
24°FOct 22Oct 27Nov 1Nov 4Nov 9Nov 13Nov 17Nov 22Nov 27
20°FNov 2Nov 9Nov 14Nov 18Nov 22Nov 26Dec 1Dec 5Dec 12
16°FNov 14Nov 22Nov 27Dec 1Dec 5Dec 9Dec 14Dec 20Dec 30

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°F172166161157154151146142130
32°F193186180177173169164160154
28°F219210204198193189184178171
24°F252241234227222216209203194
20°F286275267261255248241234224
16°F327315306298291284277268256

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
4,755
Cooling degree days, base 65°F
373
Growing degree days, base 40°F
5,160
Growing degree days, base 45°F
3,801
Growing degree days, base 50°F
2,657
Growing degree days, base 55°F
1,702
Growing degree days, base 60°F
935

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January87001
February70103
March603030
April4040105
May19619297
June20113543
July10128583
August1785533
September9627382
October3461156
November624025
December86801

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 1.2 km from High Rolls. 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 USC00295960 (Mtn Park). Public domain.