Shell Lake climate

Shell Lake Frost Dates and Growing Season

NOAA 1991-2020 normals for Spooner Ag Res Stn, 10.1 km from Shell Lake, elevation 1100 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Spooner Ag Res Stn. 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 14 and the first fall freeze around September 28, a growing season of about 135 days.

Median at 36°F
last May 26, first September 19
Median at 32°F
last May 14, first September 28
Median at 28°F
last May 2, first October 7

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 9Jun 4Jun 1May 29May 26May 24May 20May 16May 11
32°FMay 29May 25May 21May 17May 14May 10May 7May 4Apr 30
28°FMay 19May 13May 8May 5May 2Apr 30Apr 28Apr 25Apr 20
24°FMay 8May 2Apr 30Apr 26Apr 23Apr 20Apr 17Apr 14Apr 9
20°FApr 28Apr 23Apr 20Apr 17Apr 13Apr 10Apr 7Apr 4Mar 31
16°FApr 20Apr 14Apr 10Apr 7Apr 4Apr 2Mar 31Mar 27Mar 21

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 4Sep 9Sep 13Sep 16Sep 19Sep 21Sep 24Sep 27Oct 1
32°FSep 14Sep 19Sep 22Sep 25Sep 28Oct 1Oct 3Oct 7Oct 11
28°FSep 22Sep 28Oct 1Oct 4Oct 7Oct 10Oct 14Oct 19Oct 23
24°FOct 3Oct 9Oct 13Oct 18Oct 21Oct 24Oct 27Oct 31Nov 4
20°FOct 17Oct 23Oct 27Oct 30Nov 1Nov 3Nov 6Nov 10Nov 15
16°FOct 29Nov 1Nov 3Nov 6Nov 9Nov 12Nov 16Nov 19Nov 24

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°F13412812211711310910510092
32°F156149144140135132127120113
28°F176170164160156152146140134
24°F200192187183179174169164156
20°F220213208204199195191186179
16°F237231226222218214211205199

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
8,673
Cooling degree days, base 65°F
400
Growing degree days, base 40°F
3,985
Growing degree days, base 45°F
3,025
Growing degree days, base 50°F
2,182
Growing degree days, base 55°F
1,454
Growing degree days, base 60°F
852

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,68000
February1,38900
March1,12905
April681141
May32419209
June8380448
July26151590
August45112532
September22235286
October599266
November1,02305
December1,47400

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 10.1 km from Shell Lake. 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 USC00478027 (Spooner Ag Res Stn). Public domain.