Coconino County climate

Coconino County Frost Dates and Growing Season

NOAA 1991-2020 normals for Grand Canyon E Entrance, 22.5 km from Coconino County, elevation 7480 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Grand Canyon E Entrance. 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 10 and the first fall freeze around October 20, a growing season of about 165 days.

Median at 36°F
last May 20, first October 10
Median at 32°F
last May 10, first October 20
Median at 28°F
last April 26, first November 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 1May 29May 26May 23May 20May 17May 14May 10May 5
32°FMay 24May 20May 16May 13May 10May 6May 3Apr 30Apr 23
28°FMay 14May 8May 3Apr 30Apr 26Apr 21Apr 17Apr 11Apr 4
24°FApr 30Apr 21Apr 16Apr 10Apr 6Apr 3Mar 30Mar 23Mar 16
20°FApr 10Apr 3Mar 28Mar 21Mar 16Mar 12Mar 7Mar 2Feb 20
16°FMar 24Mar 15Mar 9Mar 4Feb 28Feb 23Feb 17Feb 11Feb 2

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 28Oct 1Oct 4Oct 7Oct 10Oct 13Oct 15Oct 18Oct 23
32°FOct 7Oct 12Oct 14Oct 17Oct 20Oct 24Oct 27Oct 31Nov 5
28°FOct 18Oct 23Oct 27Oct 30Nov 2Nov 5Nov 8Nov 11Nov 16
24°FOct 28Nov 2Nov 6Nov 10Nov 13Nov 16Nov 18Nov 22Nov 27
20°FNov 6Nov 12Nov 16Nov 19Nov 22Nov 25Nov 29Dec 2Dec 8
16°FNov 16Nov 21Nov 26Nov 30Dec 3Dec 6Dec 10Dec 15Dec 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°F162155150146143139134130124
32°F185179174169165160155150143
28°F215206200194189184179173164
24°F245237230224218212206199190
20°F276266259254248242234227219
16°F310297289283277271265257245

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
5,911
Cooling degree days, base 65°F
531
Growing degree days, base 40°F
4,681
Growing degree days, base 45°F
3,520
Growing degree days, base 50°F
2,535
Growing degree days, base 55°F
1,725
Growing degree days, base 60°F
1,051

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,01500
February86400
March76705
April557042
May32812200
June47116520
July8209666
August30151586
September11642379
October4152124
November735012
December1,02901

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 22.5 km from Coconino 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 USC00023584 (Grand Canyon E Entrance). Public domain.