Whiteriver climate

Whiteriver Frost Dates and Growing Season

NOAA 1991-2020 normals for Pinetop 2E, 32.1 km from Whiteriver, elevation 7200 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Pinetop 2E. 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 October 6, a growing season of about 138 days.

Median at 36°F
last June 3, first September 30
Median at 32°F
last May 22, first October 6
Median at 28°F
last May 5, first October 17

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 10Jun 7Jun 5Jun 3May 31May 30May 26May 21
32°FJun 4Jun 1May 28May 25May 22May 19May 15May 11May 6
28°FMay 23May 17May 13May 9May 5May 2Apr 30Apr 26Apr 21
24°FMay 9May 2Apr 28Apr 24Apr 19Apr 15Apr 11Apr 6Apr 2
20°FApr 21Apr 13Apr 8Apr 4Mar 31Mar 27Mar 21Mar 15Mar 8
16°FApr 6Mar 29Mar 23Mar 17Mar 12Mar 8Mar 3Feb 25Feb 16

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 17Sep 22Sep 25Sep 28Sep 30Oct 1Oct 3Oct 5Oct 9
32°FSep 24Sep 30Oct 2Oct 4Oct 6Oct 9Oct 12Oct 15Oct 19
28°FOct 4Oct 7Oct 11Oct 14Oct 17Oct 19Oct 22Oct 26Oct 31
24°FOct 14Oct 19Oct 23Oct 27Oct 30Nov 2Nov 5Nov 10Nov 16
20°FOct 23Oct 30Nov 3Nov 7Nov 12Nov 16Nov 19Nov 23Nov 28
16°FNov 3Nov 11Nov 18Nov 21Nov 24Nov 27Dec 1Dec 4Dec 10

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°F135128125121118114111106100
32°F158151146142138135130126120
28°F185178173168164159155149141
24°F218208202197192187181174166
20°F254245238232226220214207197
16°F286274266260254248242234226

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
5,926
Cooling degree days, base 65°F
202
Growing degree days, base 40°F
4,257
Growing degree days, base 45°F
3,077
Growing degree days, base 50°F
2,095
Growing degree days, base 55°F
1,285
Growing degree days, base 60°F
644

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,00800
February84101
March75507
April540040
May3224183
June7146425
July1787535
August3355487
September13811325
October451086
November72808
December1,02300

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 32.1 km from Whiteriver. 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 USC00026601 (Pinetop 2E). Public domain.