Simpsonville climate

Simpsonville Frost Dates and Growing Season

NOAA 1991-2020 normals for Shelbyville 1 E, 13.8 km from Simpsonville, elevation 730 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Shelbyville 1 E. 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 May 1 and the first fall freeze around October 10, a growing season of about 161 days.

Median at 36°F
last May 9, first October 1
Median at 32°F
last May 1, first October 10
Median at 28°F
last April 24, first October 21

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 25May 19May 14May 11May 9May 6May 3May 1Apr 28
32°FMay 15May 9May 6May 3May 1Apr 30Apr 26Apr 23Apr 19
28°FMay 7May 2Apr 29Apr 26Apr 24Apr 20Apr 18Apr 14Apr 10
24°FApr 30Apr 23Apr 19Apr 16Apr 13Apr 11Apr 7Apr 3Mar 30
20°FApr 18Apr 13Apr 8Apr 4Apr 1Mar 30Mar 26Mar 21Mar 14
16°FApr 5Mar 31Mar 27Mar 23Mar 19Mar 16Mar 13Mar 8Feb 28

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 15Sep 20Sep 23Sep 27Oct 1Oct 3Oct 5Oct 9Oct 14
32°FSep 24Oct 1Oct 4Oct 7Oct 10Oct 13Oct 16Oct 20Oct 25
28°FOct 4Oct 10Oct 15Oct 18Oct 21Oct 24Oct 27Oct 31Nov 4
24°FOct 16Oct 22Oct 26Oct 29Nov 1Nov 2Nov 5Nov 8Nov 12
20°FOct 29Nov 1Nov 3Nov 6Nov 9Nov 11Nov 14Nov 18Nov 24
16°FNov 4Nov 10Nov 14Nov 17Nov 21Nov 25Nov 29Dec 4Dec 11

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°F162155151147143139136130122
32°F181174170166161158154149142
28°F199192187183179176171167160
24°F220212207204199196192187180
20°F243237231227223218214209202
16°F273263257251246241237230222

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
5,147
Cooling degree days, base 65°F
976
Growing degree days, base 40°F
5,893
Growing degree days, base 45°F
4,621
Growing degree days, base 50°F
3,491
Growing degree days, base 55°F
2,509
Growing degree days, base 60°F
1,670

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,05409
February86207
March690242
April38312162
May13475411
June16218652
July1309773
August6245703
September80100470
October33015201
November659150
December933011

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 13.8 km from Simpsonville. 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 USC00157324 (Shelbyville 1 E). Public domain.