Arco climate

Arco Frost Dates and Growing Season

NOAA 1991-2020 normals for Arco, 0.2 km from Arco, elevation 5325 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Arco. 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 22 and the first fall freeze around September 22, a growing season of about 119 days.

Median at 36°F
last June 7, first September 10
Median at 32°F
last May 22, first September 22
Median at 28°F
last May 6, first October 3

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 28Jun 21Jun 16Jun 11Jun 7Jun 4May 31May 28May 22
32°FJun 9Jun 3May 30May 26May 22May 19May 15May 11May 5
28°FMay 24May 18May 14May 10May 6May 4May 1Apr 28Apr 20
24°FMay 8May 3Apr 30Apr 27Apr 23Apr 19Apr 15Apr 11Apr 6
20°FApr 27Apr 19Apr 14Apr 9Apr 5Apr 2Mar 30Mar 23Mar 16
16°FApr 11Apr 4Mar 30Mar 25Mar 20Mar 15Mar 12Mar 8Mar 5

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 25Aug 31Sep 4Sep 7Sep 10Sep 13Sep 16Sep 20Sep 26
32°FSep 4Sep 9Sep 15Sep 18Sep 22Sep 26Sep 29Oct 3Oct 7
28°FSep 16Sep 22Sep 27Sep 30Oct 3Oct 6Oct 10Oct 15Oct 19
24°FSep 28Oct 4Oct 9Oct 13Oct 16Oct 19Oct 22Oct 25Oct 30
20°FOct 11Oct 17Oct 22Oct 25Oct 28Oct 30Nov 2Nov 5Nov 10
16°FOct 20Oct 26Oct 31Nov 2Nov 6Nov 8Nov 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°F117108102979287827665
32°F14213512912411911410810292
28°F169162156151146141137132124
24°F200191184179175169164159151
20°F228220214208204198193187177
16°F251244239234228223216209201

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
8,053
Cooling degree days, base 65°F
313
Growing degree days, base 40°F
3,715
Growing degree days, base 45°F
2,744
Growing degree days, base 50°F
1,923
Growing degree days, base 55°F
1,246
Growing degree days, base 60°F
705

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,43700
February1,17000
March95001
April636021
May3824142
June15335338
July27154592
August40106532
September22514256
October620042
November1,02500
December1,38700

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 0.2 km from Arco. 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 USC00100375 (Arco). Public domain.