Shonto climate

Shonto Frost Dates and Growing Season

NOAA 1991-2020 normals for Betatakin, 13 km from Shonto, elevation 7286 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Betatakin. 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 7 and the first fall freeze around October 15, a growing season of about 159 days.

Median at 36°F
last May 20, first October 6
Median at 32°F
last May 7, first October 15
Median at 28°F
last April 28, first October 27

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 6Jun 1May 29May 23May 20May 16May 12May 8May 3
32°FMay 26May 20May 14May 10May 7May 4May 1Apr 28Apr 23
28°FMay 12May 7May 3May 1Apr 28Apr 24Apr 21Apr 17Apr 11
24°FMay 2Apr 26Apr 22Apr 17Apr 14Apr 10Apr 6Apr 1Mar 22
20°FApr 16Apr 10Apr 5Mar 31Mar 25Mar 17Mar 12Mar 6Feb 26
16°FApr 1Mar 17Mar 9Mar 5Feb 28Feb 24Feb 19Feb 13Feb 3

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 21Sep 28Oct 1Oct 3Oct 6Oct 9Oct 13Oct 16Oct 22
32°FSep 30Oct 4Oct 8Oct 12Oct 15Oct 18Oct 23Oct 27Nov 1
28°FOct 7Oct 15Oct 19Oct 23Oct 27Oct 30Nov 3Nov 7Nov 13
24°FOct 18Oct 24Oct 29Nov 3Nov 7Nov 10Nov 14Nov 18Nov 22
20°FOct 30Nov 6Nov 11Nov 15Nov 18Nov 21Nov 24Nov 27Dec 3
16°FNov 10Nov 17Nov 20Nov 24Nov 27Nov 30Dec 4Dec 8Dec 15

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°F159152146141136132127121113
32°F183175169164159155149142133
28°F207198193187183178172165155
24°F232223216211205200195188179
20°F270260250244237230224216206
16°F304292285278272265259251239

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
5,735
Cooling degree days, base 65°F
654
Growing degree days, base 40°F
5,016
Growing degree days, base 45°F
3,843
Growing degree days, base 50°F
2,825
Growing degree days, base 55°F
1,954
Growing degree days, base 60°F
1,229

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,05600
February86401
March733014
April513068
May25322263
June41142551
July6251710
August10182637
September8755421
October3882146
November737015
December1,04800

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 13 km from Shonto. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00020750 (Betatakin). Public domain.