Smith County climate

Smith County Frost Dates and Growing Season

NOAA 1991-2020 normals for Smith Ctr, 1 km from Smith County, elevation 1820 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Smith Ctr. 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 24 and the first fall freeze around October 15, a growing season of about 173 days.

Median at 36°F
last May 3, first October 5
Median at 32°F
last April 24, first October 15
Median at 28°F
last April 13, first October 24

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 16May 11May 8May 6May 3May 1Apr 29Apr 26Apr 22
32°FMay 7May 2Apr 30Apr 27Apr 24Apr 21Apr 18Apr 14Apr 9
28°FApr 28Apr 23Apr 20Apr 17Apr 13Apr 10Apr 7Apr 4Mar 31
24°FApr 20Apr 15Apr 10Apr 7Apr 4Apr 1Mar 29Mar 25Mar 20
20°FApr 11Apr 6Apr 2Mar 30Mar 27Mar 23Mar 18Mar 14Mar 7
16°FApr 3Mar 29Mar 23Mar 19Mar 15Mar 11Mar 7Mar 3Feb 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 22Sep 27Sep 30Oct 3Oct 5Oct 8Oct 11Oct 15Oct 19
32°FSep 28Oct 4Oct 8Oct 11Oct 15Oct 18Oct 21Oct 23Oct 28
28°FOct 6Oct 14Oct 18Oct 21Oct 24Oct 27Oct 30Nov 1Nov 6
24°FOct 18Oct 24Oct 27Oct 31Nov 2Nov 4Nov 7Nov 11Nov 15
20°FOct 27Nov 1Nov 4Nov 7Nov 10Nov 13Nov 16Nov 19Nov 25
16°FNov 1Nov 6Nov 11Nov 14Nov 17Nov 22Nov 26Nov 30Dec 5

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°F172166162158154151148143138
32°F193186181176173169165160152
28°F212205201196192188184179172
24°F233225219214210207202197191
20°F251244239234229224220214207
16°F271262257252247243237231224

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
5,645
Cooling degree days, base 65°F
1,342
Growing degree days, base 40°F
6,113
Growing degree days, base 45°F
4,904
Growing degree days, base 50°F
3,826
Growing degree days, base 55°F
2,873
Growing degree days, base 60°F
2,044

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,16900
February94505
March725143
April40610148
May14683411
June11282721
July0437902
August3352814
September66158544
October34819208
November734029
December1,09301

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 1 km from Smith County. 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 USC00147542 (Smith Ctr). Public domain.