Sullivan climate

Sullivan Frost Dates and Growing Season

NOAA 1991-2020 normals for Union, 29.6 km from Sullivan, elevation 540 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Union. 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 23, a growing season of about 194 days.

Median at 36°F
last April 22, first October 13
Median at 32°F
last April 11, first October 23
Median at 28°F
last March 31, first November 3

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 8May 4Apr 30Apr 26Apr 22Apr 19Apr 16Apr 13Apr 8
32°FApr 28Apr 21Apr 17Apr 14Apr 11Apr 7Apr 5Mar 31Mar 26
28°FApr 15Apr 9Apr 5Apr 2Mar 31Mar 28Mar 24Mar 19Mar 12
24°FApr 3Mar 30Mar 26Mar 22Mar 18Mar 15Mar 11Mar 7Mar 1
20°FMar 25Mar 19Mar 15Mar 11Mar 8Mar 5Mar 1Feb 26Feb 17
16°FMar 17Mar 11Mar 7Mar 3Feb 28Feb 24Feb 20Feb 14Feb 5

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 5Oct 7Oct 10Oct 13Oct 16Oct 19Oct 22Oct 26
32°FOct 9Oct 14Oct 18Oct 21Oct 23Oct 26Oct 29Nov 1Nov 5
28°FOct 21Oct 26Oct 30Nov 1Nov 3Nov 5Nov 9Nov 12Nov 18
24°FNov 1Nov 4Nov 8Nov 11Nov 14Nov 17Nov 21Nov 25Dec 1
20°FNov 8Nov 14Nov 18Nov 22Nov 26Nov 30Dec 3Dec 7Dec 13
16°FNov 17Nov 24Nov 30Dec 4Dec 7Dec 11Dec 17Dec 22Dec 28

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°F193186181176172168163158152
32°F216207202198194190186181173
28°F239232226222217213209204197
24°F263256251246241237232226219
20°F290279273267263258252247239
16°F313303296290284279273267257

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
4,400
Cooling degree days, base 65°F
1,485
Growing degree days, base 40°F
6,915
Growing degree days, base 45°F
5,550
Growing degree days, base 50°F
4,333
Growing degree days, base 55°F
3,246
Growing degree days, base 60°F
2,293

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January99307
February779115
March558694
April25435265
May72117511
June5297742
July0434899
August1391855
September42173581
October24929272
November568376
December879015

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 29.6 km from Sullivan. 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 USC00238515 (Union). Public domain.