Tonto Basin climate

Tonto Basin Frost Dates and Growing Season

NOAA 1991-2020 normals for Punkin Ctr, 2.8 km from Tonto Basin, elevation 2325 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Punkin Ctr. 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 March 7 and the first fall freeze around November 20, a growing season of about 255 days.

Median at 36°F
last March 27, first November 10
Median at 32°F
last March 7, first November 20
Median at 28°F
last February 15, first December 1

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°FApr 16Apr 8Apr 3Mar 31Mar 27Mar 23Mar 20Mar 16Mar 11
32°FMar 27Mar 19Mar 14Mar 10Mar 7Mar 4Mar 1Feb 24Feb 13
28°FMar 7Mar 2Feb 26Feb 20Feb 15Feb 9Feb 3Jan 31Jan 20
24°FFeb 21Feb 12Feb 5Jan 31Jan 26Jan 19Jan 12Jan 6Dec 28
20°FFeb 6Jan 30Jan 20Jan 13Jan 9Jan 3Dec 30Dec 24Dec 18
16°FJan 31Jan 29Jan 20Jan 16Jan 8Jan 5Jan 3Jan 2Dec 26

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 25Oct 31Nov 4Nov 6Nov 10Nov 13Nov 15Nov 18Nov 22
32°FNov 3Nov 10Nov 14Nov 17Nov 20Nov 22Nov 25Nov 29Dec 3
28°FNov 16Nov 21Nov 25Nov 27Dec 1Dec 4Dec 7Dec 11Dec 17
24°FNov 27Dec 2Dec 7Dec 11Dec 15Dec 19Dec 22Dec 27Jan 5
20°FDec 10Dec 15Dec 21Dec 25Dec 28Dec 31Jan 5Jan 13Jan 27
16°FDec 26Jan 1Jan 2Jan 4Jan 8Jan 14Jan 18Jan 28Jan 31

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°F248241235229224219214209200
32°F281271266260255250244238228
28°F316307299292286281276269262
24°F353343336330323317310302290
20°F365365365365359353346338329
16°F365365365365365365365365363

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
97% of years
20°F or colder
59% of years
16°F or colder
11% 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
2,257
Cooling degree days, base 65°F
2,766
Growing degree days, base 40°F
9,651
Growing degree days, base 45°F
7,913
Growing degree days, base 50°F
6,341
Growing degree days, base 55°F
4,980
Growing degree days, base 60°F
3,794

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January564021
February395074
March2507234
April9857412
May16238687
June1506956
July07041,169
August06601,125
September0453903
October42135559
November2946188
December596015

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 2.8 km from Tonto Basin. 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 USC00026840 (Punkin Ctr). Public domain.