First Mesa climate

First Mesa Frost Dates and Growing Season

NOAA 1991-2020 normals for Keams Canyon, 17.2 km from First Mesa, elevation 6205 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Keams Canyon. 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 16 and the first fall freeze around October 10, a growing season of about 147 days.

Median at 36°F
last June 1, first October 2
Median at 32°F
last May 16, first October 10
Median at 28°F
last May 1, first October 20

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 15Jun 9Jun 6Jun 3Jun 1May 29May 24May 19May 14
32°FJun 5May 31May 25May 19May 16May 12May 8May 3Apr 29
28°FMay 20May 13May 9May 4May 1Apr 28Apr 24Apr 20Apr 14
24°FMay 8May 1Apr 26Apr 21Apr 17Apr 12Apr 8Apr 4Mar 28
20°FApr 24Apr 14Apr 8Apr 3Mar 29Mar 23Mar 18Mar 13Mar 6
16°FMar 31Mar 21Mar 15Mar 11Mar 7Mar 4Feb 28Feb 23Feb 13

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 22Sep 25Sep 28Oct 1Oct 2Oct 5Oct 7Oct 10Oct 15
32°FSep 29Oct 2Oct 5Oct 7Oct 10Oct 13Oct 16Oct 19Oct 24
28°FOct 6Oct 11Oct 15Oct 17Oct 20Oct 24Oct 28Nov 1Nov 5
24°FOct 15Oct 20Oct 25Oct 29Nov 1Nov 4Nov 6Nov 10Nov 14
20°FOct 24Oct 31Nov 3Nov 7Nov 11Nov 13Nov 17Nov 19Nov 24
16°FNov 2Nov 10Nov 14Nov 17Nov 19Nov 22Nov 25Nov 28Dec 3

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°F146138132128124120116112105
32°F169160155151147142136130123
28°F191184179174169166161156146
24°F220210204198194189184178170
20°F251242235230223217211203194
16°F280271265259254249244235226

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
5,722
Cooling degree days, base 65°F
556
Growing degree days, base 40°F
4,849
Growing degree days, base 45°F
3,659
Growing degree days, base 50°F
2,647
Growing degree days, base 55°F
1,797
Growing degree days, base 60°F
1,099

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,04800
February82300
March70708
April487063
May2619231
June5187486
July1250714
August5173632
September9337397
October4230107
November74408
December1,07800

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 17.2 km from First Mesa. 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 USC00024586 (Keams Canyon). Public domain.