Arthur County climate

Arthur County Frost Dates and Growing Season

NOAA 1991-2020 normals for Arthur, 0.4 km from Arthur County, elevation 3660 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Arthur. 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 9 and the first fall freeze around October 3, a growing season of about 144 days.

Median at 36°F
last May 20, first September 26
Median at 32°F
last May 9, first October 3
Median at 28°F
last April 30, first October 12

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 3May 30May 26May 23May 20May 17May 15May 12May 8
32°FMay 22May 17May 15May 12May 9May 7May 4May 2Apr 29
28°FMay 11May 7May 5May 2Apr 30Apr 28Apr 24Apr 20Apr 15
24°FMay 2Apr 29Apr 25Apr 22Apr 19Apr 15Apr 12Apr 8Apr 2
20°FApr 23Apr 18Apr 14Apr 10Apr 7Apr 4Mar 31Mar 26Mar 20
16°FApr 13Apr 7Apr 3Mar 31Mar 27Mar 23Mar 18Mar 14Mar 8

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 20Sep 23Sep 26Sep 28Oct 1Oct 3Oct 6
32°FSep 20Sep 25Sep 28Oct 1Oct 3Oct 5Oct 8Oct 11Oct 16
28°FSep 28Oct 2Oct 6Oct 8Oct 12Oct 15Oct 17Oct 20Oct 23
24°FOct 6Oct 12Oct 16Oct 18Oct 20Oct 23Oct 25Oct 27Nov 1
20°FOct 15Oct 18Oct 22Oct 24Oct 27Oct 30Nov 1Nov 6Nov 11
16°FOct 21Oct 26Oct 30Nov 2Nov 5Nov 9Nov 12Nov 16Nov 21

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°F142137134130126122119114108
32°F161155151148144141137133128
28°F183176172168165162157152145
24°F204197192189184180176171166
20°F224216211206202198194189182
16°F246238232227222217212205198

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
6,645
Cooling degree days, base 65°F
780
Growing degree days, base 40°F
4,929
Growing degree days, base 45°F
3,821
Growing degree days, base 50°F
2,858
Growing degree days, base 55°F
2,037
Growing degree days, base 60°F
1,343

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,21500
February1,02102
March833020
April552277
May27030265
June53144543
July7288747
August16234684
September14080402
October5083105
November854013
December1,17900

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 0.4 km from Arthur County. 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 USC00250365 (Arthur). Public domain.