Graham climate

Graham Frost Dates and Growing Season

NOAA 1991-2020 normals for Mcmillin Rsvr, 9.7 km from Graham, elevation 579 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mcmillin Rsvr. 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 11 and the first fall freeze around October 30, a growing season of about 202 days.

Median at 36°F
last May 1, first October 12
Median at 32°F
last April 11, first October 30
Median at 28°F
last March 16, first November 14

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 17May 12May 7May 4May 1Apr 29Apr 26Apr 23Apr 17
32°FApr 29Apr 24Apr 19Apr 15Apr 11Apr 7Apr 3Mar 30Mar 23
28°FApr 8Apr 1Mar 27Mar 22Mar 16Mar 10Mar 4Feb 27Feb 19
24°FMar 16Mar 5Feb 28Feb 24Feb 19Feb 13Feb 3Jan 16Dec 31
20°FFeb 25Feb 18Feb 10Feb 1Jan 19Jan 4Dec 30Dec 16Dec 5
16°FFeb 17Feb 6Jan 31Jan 11Jan 2Dec 24Dec 13Dec 6Nov 30

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 30Oct 3Oct 5Oct 9Oct 12Oct 16Oct 19Oct 24Oct 31
32°FOct 13Oct 19Oct 22Oct 26Oct 30Nov 1Nov 5Nov 10Nov 17
28°FOct 28Nov 1Nov 6Nov 10Nov 14Nov 19Nov 24Nov 30Dec 8
24°FNov 8Nov 14Nov 22Nov 27Dec 1Dec 6Dec 12Dec 27Jan 9
20°FNov 18Nov 28Dec 2Dec 9Dec 15Dec 25Jan 1Jan 15Feb 5
16°FNov 23Dec 1Dec 6Dec 13Dec 22Jan 1Jan 13Feb 1Feb 12

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°F186178172167163159155150142
32°F226217212206202197191185177
28°F279267257251244238231223213
24°F339323311301291283274264252
20°F365365359348336330321310299
16°F365365365365365365353337324

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
98% of years
20°F or colder
72% of years
16°F or colder
37% 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
5,397
Cooling degree days, base 65°F
120
Growing degree days, base 40°F
4,135
Growing degree days, base 45°F
2,766
Growing degree days, base 50°F
1,715
Growing degree days, base 55°F
938
Growing degree days, base 60°F
406

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January78402
February68502
March650010
April510038
May3313155
June19212271
July7848436
August6349451
September1918269
October453071
November65409
December80702

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 9.7 km from Graham. 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 USC00455224 (Mcmillin Rsvr). Public domain.