Thomson climate

Thomson Frost Dates and Growing Season

NOAA 1991-2020 normals for Thomson 1.5SE, 3.1 km from Thomson, elevation 542 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Thomson 1.5SE. 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 March 14 and the first fall freeze around November 17, a growing season of about 252 days.

Median at 36°F
last March 27, first November 6
Median at 32°F
last March 14, first November 17
Median at 28°F
last February 26, first December 4

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°FApr 12Apr 6Apr 3Mar 31Mar 27Mar 24Mar 20Mar 16Mar 9
32°FMar 31Mar 26Mar 21Mar 17Mar 14Mar 10Mar 5Feb 28Feb 21
28°FMar 19Mar 14Mar 7Mar 2Feb 26Feb 21Feb 15Feb 8Jan 31
24°FMar 8Feb 28Feb 20Feb 14Feb 8Feb 2Jan 29Jan 21Jan 9
20°FFeb 27Feb 14Feb 7Feb 1Jan 30Jan 24Jan 16Jan 9Jan 2
16°FFeb 12Feb 5Jan 31Jan 29Jan 23Jan 18Jan 15Jan 10Jan 4

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 25Oct 30Nov 1Nov 4Nov 6Nov 9Nov 11Nov 15Nov 21
32°FNov 3Nov 7Nov 11Nov 14Nov 17Nov 21Nov 26Dec 1Dec 8
28°FNov 14Nov 19Nov 25Dec 1Dec 4Dec 9Dec 18Dec 28Jan 5
24°FNov 30Dec 8Dec 16Dec 24Dec 31Jan 4Jan 9Jan 15Jan 26
20°FDec 20Dec 28Jan 2Jan 6Jan 11Jan 16Jan 21Jan 29Feb 5
16°FJan 1Jan 7Jan 11Jan 15Jan 18Jan 23Jan 29Feb 1Feb 8

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°F249241235230225220216211203
32°F281271263257252246240235227
28°F319307299291284277270263251
24°F353341333326318311305298285
20°F365365364353344337332322309
16°F365365365365365365359344333

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
95% of years
20°F or colder
69% of years
16°F or colder
32% 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
2,461
Cooling degree days, base 65°F
1,965
Growing degree days, base 40°F
8,709
Growing degree days, base 45°F
7,022
Growing degree days, base 50°F
5,482
Growing degree days, base 55°F
4,114
Growing degree days, base 60°F
2,947

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January600052
February484159
March3259188
April9244403
May17200648
June0384834
July0491956
August0452917
September7301743
October8079466
November3264149
December531067

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 3.1 km from Thomson. 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 USC00098677 (Thomson 1.5SE). Public domain.