Granite climate

Granite Frost Dates and Growing Season

NOAA 1991-2020 normals for Altus Dam, 11.5 km from Granite, elevation 1525 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Altus Dam. 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 2 and the first fall freeze around November 3, a growing season of about 213 days.

Median at 36°F
last April 14, first October 26
Median at 32°F
last April 2, first November 3
Median at 28°F
last March 21, first November 12

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 30Apr 24Apr 21Apr 17Apr 14Apr 10Apr 7Apr 3Mar 28
32°FApr 21Apr 15Apr 10Apr 6Apr 2Mar 30Mar 25Mar 19Mar 11
28°FApr 8Apr 3Mar 30Mar 26Mar 21Mar 16Mar 11Mar 5Feb 28
24°FMar 30Mar 22Mar 16Mar 10Mar 6Mar 3Feb 28Feb 23Feb 16
20°FMar 15Mar 8Mar 3Feb 28Feb 25Feb 20Feb 15Feb 9Jan 31
16°FMar 6Mar 1Feb 24Feb 16Feb 10Feb 5Jan 30Jan 23Jan 12

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 10Oct 17Oct 20Oct 24Oct 26Oct 29Nov 1Nov 3Nov 7
32°FOct 18Oct 24Oct 29Nov 1Nov 3Nov 5Nov 9Nov 13Nov 18
28°FOct 25Nov 1Nov 4Nov 8Nov 12Nov 15Nov 19Nov 24Nov 29
24°FNov 2Nov 8Nov 13Nov 18Nov 22Nov 26Nov 29Dec 2Dec 9
20°FNov 11Nov 20Nov 25Nov 28Dec 2Dec 5Dec 10Dec 15Dec 23
16°FNov 24Dec 1Dec 5Dec 11Dec 17Dec 23Dec 30Jan 4Jan 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°F216208204199194190185180172
32°F240231223219213209204198191
28°F261251246240235230224218210
24°F284276269263257251246239229
20°F313303295289282275269262252
16°F343332324316310304297288276

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
98% 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
3,569
Cooling degree days, base 65°F
2,210
Growing degree days, base 40°F
8,176
Growing degree days, base 45°F
6,692
Growing degree days, base 50°F
5,353
Growing degree days, base 55°F
4,159
Growing degree days, base 60°F
3,113

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January818015
February636139
March44211150
April19751329
May51197612
June2431879
July05861,051
August15451,009
September19302734
October16282402
November4735114
December769021

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 11.5 km from Granite. 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 USC00340184 (Altus Dam). Public domain.