Hartley climate

Hartley Frost Dates and Growing Season

NOAA 1991-2020 normals for Hartley, 1.4 km from Hartley, elevation 3887 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hartley. 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 22 and the first fall freeze around October 24, a growing season of about 183 days.

Median at 36°F
last May 1, first October 14
Median at 32°F
last April 22, first October 24
Median at 28°F
last April 11, first November 1

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 14May 10May 7May 4May 1Apr 30Apr 27Apr 23Apr 18
32°FMay 5May 1Apr 29Apr 25Apr 22Apr 19Apr 16Apr 12Apr 7
28°FApr 27Apr 22Apr 18Apr 14Apr 11Apr 8Apr 4Mar 31Mar 26
24°FApr 15Apr 9Apr 5Apr 2Mar 31Mar 27Mar 22Mar 17Mar 10
20°FApr 6Mar 31Mar 26Mar 21Mar 17Mar 14Mar 8Mar 4Feb 28
16°FMar 24Mar 17Mar 12Mar 7Mar 4Mar 1Feb 26Feb 21Feb 15

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 1Oct 5Oct 8Oct 11Oct 14Oct 17Oct 19Oct 22Oct 25
32°FOct 11Oct 16Oct 19Oct 22Oct 24Oct 26Oct 28Oct 31Nov 3
28°FOct 21Oct 25Oct 28Oct 31Nov 1Nov 4Nov 6Nov 9Nov 12
24°FOct 28Nov 1Nov 4Nov 7Nov 10Nov 12Nov 15Nov 18Nov 22
20°FNov 3Nov 8Nov 11Nov 14Nov 17Nov 20Nov 23Nov 27Dec 3
16°FNov 10Nov 15Nov 20Nov 24Nov 27Dec 1Dec 3Dec 8Dec 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°F180175171166163159156152146
32°F203196191187183180175171165
28°F224217212208204200196191184
24°F248240234229225220216210204
20°F269262256251246241236230222
16°F292284279272268263257251241

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
4,558
Cooling degree days, base 65°F
1,220
Growing degree days, base 40°F
6,436
Growing degree days, base 45°F
5,067
Growing degree days, base 50°F
3,871
Growing degree days, base 55°F
2,843
Growing degree days, base 60°F
1,959

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January92102
February749014
March577164
April34010179
May12378426
June7247690
July0391855
August2331793
September42142551
October27321247
November609045
December91404

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 1.4 km from Hartley. 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 USC00413979 (Hartley). Public domain.