Thompson climate

Thompson Frost Dates and Growing Season

NOAA 1991-2020 normals for W Thompson Lake, 3.7 km from Thompson, elevation 360 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for W Thompson Lake. 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 9, a growing season of about 161 days.

Median at 36°F
last May 14, first October 1
Median at 32°F
last May 1, first October 9
Median at 28°F
last April 19, 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 31May 25May 20May 17May 14May 11May 8May 4May 1
32°FMay 17May 11May 7May 3May 1Apr 29Apr 27Apr 24Apr 20
28°FMay 2Apr 28Apr 25Apr 22Apr 19Apr 17Apr 14Apr 10Apr 5
24°FApr 19Apr 15Apr 11Apr 8Apr 6Apr 3Apr 1Mar 29Mar 23
20°FApr 6Apr 3Mar 31Mar 30Mar 26Mar 23Mar 19Mar 15Mar 10
16°FMar 31Mar 26Mar 22Mar 18Mar 16Mar 13Mar 10Mar 6Mar 1

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

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°F155150145142138135131127119
32°F181174169164161157153148140
28°F205198193188184181176171164
24°F231223218213209206201196189
20°F259251245240236231226220213
16°F282274269264259254250245238

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
6,582
Cooling degree days, base 65°F
505
Growing degree days, base 40°F
4,537
Growing degree days, base 45°F
3,437
Growing degree days, base 50°F
2,489
Growing degree days, base 55°F
1,680
Growing degree days, base 60°F
1,016

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,24301
February1,06101
March93207
April565256
May27017231
June7685460
July9198654
August20150595
September14050364
October471399
November743018
December1,05402

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 3.7 km from Thompson. 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 USC00069388 (W Thompson Lake). Public domain.