Old Fort climate

Old Fort Frost Dates and Growing Season

NOAA 1991-2020 normals for Old Ft Ag 3 W, 6.7 km from Old Fort, elevation 1425 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Old Ft Ag 3 W. 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 21 and the first fall freeze around October 23, a growing season of about 183 days.

Median at 36°F
last May 4, first October 14
Median at 32°F
last April 21, first October 23
Median at 28°F
last April 7, first November 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°FMay 20May 14May 10May 7May 4May 1Apr 28Apr 23Apr 18
32°FMay 9May 3Apr 29Apr 24Apr 21Apr 18Apr 15Apr 11Apr 6
28°FApr 22Apr 17Apr 14Apr 10Apr 7Apr 4Apr 1Mar 29Mar 22
24°FApr 9Apr 4Apr 1Mar 29Mar 25Mar 20Mar 17Mar 13Mar 6
20°FMar 31Mar 25Mar 20Mar 16Mar 12Mar 8Mar 4Feb 28Feb 20
16°FMar 20Mar 14Mar 7Mar 2Feb 27Feb 22Feb 16Feb 8Jan 31

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 1Oct 5Oct 9Oct 11Oct 14Oct 16Oct 20Oct 24Oct 28
32°FOct 9Oct 14Oct 17Oct 20Oct 23Oct 26Oct 29Nov 1Nov 5
28°FOct 16Oct 21Oct 25Oct 28Nov 1Nov 2Nov 5Nov 9Nov 13
24°FOct 25Oct 31Nov 3Nov 5Nov 9Nov 12Nov 15Nov 20Nov 27
20°FNov 4Nov 10Nov 13Nov 17Nov 22Nov 26Dec 1Dec 4Dec 12
16°FNov 15Nov 22Nov 30Dec 3Dec 8Dec 13Dec 20Dec 27Jan 3

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°F182175170166162158153148142
32°F205197192187183179174169162
28°F229221215211207203199194186
24°F253246240235230225220215207
20°F283273266260255250244238228
16°F316305297291285279273264253

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
4,227
Cooling degree days, base 65°F
841
Growing degree days, base 40°F
6,158
Growing degree days, base 45°F
4,745
Growing degree days, base 50°F
3,513
Growing degree days, base 55°F
2,458
Growing degree days, base 60°F
1,568

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January86209
February703014
March570171
April2957196
May11845396
June10164604
July0270735
August1234697
September56104498
October27216231
November551151
December790011

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 6.7 km from Old Fort. 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 USC00316380 (Old Ft Ag 3 W). Public domain.