Tomah climate

Tomah Frost Dates and Growing Season

NOAA 1991-2020 normals for Mather 3 Nw, 25.1 km from Tomah, elevation 978 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mather 3 Nw. 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 6 and the first fall freeze around October 3, a growing season of about 148 days.

Median at 36°F
last May 17, first September 23
Median at 32°F
last May 6, first October 3
Median at 28°F
last April 26, first October 15

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°FJun 1May 27May 23May 20May 17May 14May 11May 9May 5
32°FMay 20May 15May 12May 9May 6May 4May 1Apr 28Apr 24
28°FMay 9May 3May 1Apr 28Apr 26Apr 23Apr 21Apr 16Apr 11
24°FApr 27Apr 22Apr 19Apr 16Apr 13Apr 10Apr 8Apr 5Apr 1
20°FApr 17Apr 13Apr 9Apr 7Apr 4Apr 2Apr 1Mar 28Mar 21
16°FApr 9Apr 5Apr 2Apr 1Mar 29Mar 26Mar 22Mar 19Mar 13

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 10Sep 14Sep 17Sep 20Sep 23Sep 26Sep 29Oct 1Oct 5
32°FSep 19Sep 25Sep 29Oct 1Oct 3Oct 5Oct 8Oct 12Oct 16
28°FOct 1Oct 5Oct 9Oct 12Oct 15Oct 18Oct 21Oct 25Oct 30
24°FOct 15Oct 19Oct 22Oct 25Oct 28Oct 30Nov 1Nov 4Nov 9
20°FOct 26Oct 30Nov 1Nov 3Nov 5Nov 8Nov 11Nov 15Nov 20
16°FNov 2Nov 6Nov 9Nov 12Nov 14Nov 18Nov 20Nov 24Nov 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°F145140135131128124120115108
32°F167160156152148145141136129
28°F191184179174171167163159152
24°F214208204200196192189184177
20°F235227222218215212208204198
16°F251243239235230226222216211

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
8,082
Cooling degree days, base 65°F
438
Growing degree days, base 40°F
4,137
Growing degree days, base 45°F
3,145
Growing degree days, base 50°F
2,274
Growing degree days, base 55°F
1,526
Growing degree days, base 60°F
907

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,55600
February1,29900
March1,07109
April648144
May30322223
June7394472
July23164606
August42118541
September20836296
October561376
November94407
December1,35600

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 25.1 km from Tomah. 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 USC00475164 (Mather 3 Nw). Public domain.