Evergreen climate

Evergreen Frost Dates and Growing Season

NOAA 1991-2020 normals for Evergreen, 0.6 km from Evergreen, elevation 6985 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Evergreen. 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 23 and the first fall freeze around September 22, a growing season of about 118 days.

Median at 36°F
last June 10, first September 11
Median at 32°F
last May 23, first September 22
Median at 28°F
last May 9, first October 2

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 26Jun 21Jun 17Jun 13Jun 10Jun 7Jun 5Jun 2May 29
32°FJun 10Jun 2May 29May 26May 23May 20May 17May 14May 9
28°FMay 22May 18May 15May 12May 9May 7May 4May 2Apr 29
24°FMay 15May 10May 6May 3Apr 30Apr 28Apr 25Apr 21Apr 16
20°FMay 7May 2Apr 30Apr 26Apr 22Apr 19Apr 16Apr 11Apr 6
16°FApr 30Apr 25Apr 20Apr 16Apr 12Apr 8Apr 5Mar 31Mar 23

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 27Sep 1Sep 5Sep 8Sep 11Sep 13Sep 16Sep 19Sep 23
32°FSep 6Sep 13Sep 16Sep 19Sep 22Sep 24Sep 27Sep 30Oct 3
28°FSep 18Sep 24Sep 27Sep 30Oct 2Oct 4Oct 7Oct 10Oct 15
24°FSep 27Oct 2Oct 5Oct 9Oct 12Oct 14Oct 17Oct 20Oct 24
20°FOct 3Oct 10Oct 14Oct 18Oct 20Oct 23Oct 26Oct 29Nov 2
16°FOct 11Oct 17Oct 22Oct 26Oct 30Nov 2Nov 4Nov 8Nov 13

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°F11110499959086817567
32°F13813112712211811511010495
28°F163156152148145141137132125
24°F183176172168164159154149142
20°F201195190185181176171166158
16°F224215209204198194189184176

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
7,467
Cooling degree days, base 65°F
99
Growing degree days, base 40°F
3,339
Growing degree days, base 45°F
2,330
Growing degree days, base 50°F
1,514
Growing degree days, base 55°F
868
Growing degree days, base 60°F
385

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,13300
February1,01100
March90102
April716010
May473193
June18313288
July5154468
August8629408
September2733209
October623034
November88102
December1,13800

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 0.6 km from Evergreen. 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 USC00052790 (Evergreen). Public domain.