Dilkon climate

Dilkon Frost Dates and Growing Season

NOAA 1991-2020 normals for Holbrook, 55 km from Dilkon, elevation 5085 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Holbrook. 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 April 22 and the first fall freeze around October 24, a growing season of about 184 days.

Median at 36°F
last May 4, first October 15
Median at 32°F
last April 22, first October 24
Median at 28°F
last April 6, 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°FMay 21May 15May 11May 7May 4May 2Apr 30Apr 27Apr 23
32°FMay 7May 2Apr 29Apr 25Apr 22Apr 20Apr 16Apr 13Apr 8
28°FApr 22Apr 17Apr 12Apr 9Apr 6Apr 3Mar 31Mar 27Mar 21
24°FApr 9Apr 3Mar 30Mar 26Mar 21Mar 17Mar 13Mar 8Mar 3
20°FMar 26Mar 17Mar 12Mar 9Mar 6Mar 3Feb 27Feb 21Feb 12
16°FMar 11Mar 5Mar 1Feb 24Feb 19Feb 15Feb 9Feb 3Jan 25

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°FOct 3Oct 6Oct 9Oct 12Oct 15Oct 17Oct 19Oct 22Oct 26
32°FOct 12Oct 16Oct 18Oct 21Oct 24Oct 27Oct 30Nov 1Nov 5
28°FOct 19Oct 24Oct 28Oct 31Nov 2Nov 4Nov 7Nov 10Nov 14
24°FOct 28Nov 2Nov 5Nov 8Nov 11Nov 13Nov 16Nov 19Nov 23
20°FNov 6Nov 11Nov 15Nov 18Nov 20Nov 23Nov 26Nov 30Dec 5
16°FNov 17Nov 21Nov 24Nov 28Dec 1Dec 4Dec 7Dec 11Dec 17

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°F179173168164161157153148141
32°F203197192188184180175170164
28°F230222216213209205201195188
24°F255248243237233228225219211
20°F283273267262257252247241232
16°F312302294289282277271265256

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
4,269
Cooling degree days, base 65°F
1,237
Growing degree days, base 40°F
6,520
Growing degree days, base 45°F
5,130
Growing degree days, base 50°F
3,920
Growing degree days, base 55°F
2,876
Growing degree days, base 60°F
1,980

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January88301
February67305
March530052
April3113173
May9955424
June7253696
July0411876
August1348812
September18157589
October23611259
November603032
December91001

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 55 km from Dilkon. 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 USC00024089 (Holbrook). Public domain.