Lower Brule climate

Lower Brule Frost Dates and Growing Season

NOAA 1991-2020 normals for Lake Sharpe Prj, 9.8 km from Lower Brule, elevation 1461 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lake Sharpe Prj. 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 5, a growing season of about 152 days.

Median at 36°F
last May 16, first September 28
Median at 32°F
last May 6, first October 5
Median at 28°F
last April 28, first October 16

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 30May 25May 22May 18May 16May 13May 11May 8May 4
32°FMay 20May 15May 11May 9May 6May 4May 2Apr 30Apr 25
28°FMay 10May 5May 3Apr 30Apr 28Apr 25Apr 22Apr 18Apr 13
24°FMay 2Apr 27Apr 24Apr 20Apr 17Apr 14Apr 12Apr 8Apr 4
20°FApr 23Apr 18Apr 14Apr 11Apr 7Apr 4Apr 2Mar 30Mar 22
16°FApr 15Apr 8Apr 4Apr 1Mar 31Mar 27Mar 22Mar 18Mar 12

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 17Sep 20Sep 23Sep 26Sep 28Oct 1Oct 3Oct 6Oct 11
32°FSep 23Sep 28Oct 1Oct 2Oct 5Oct 8Oct 11Oct 14Oct 18
28°FOct 1Oct 5Oct 10Oct 13Oct 16Oct 19Oct 21Oct 24Oct 30
24°FOct 10Oct 16Oct 19Oct 22Oct 24Oct 28Oct 31Nov 3Nov 7
20°FOct 19Oct 24Oct 28Oct 31Nov 2Nov 5Nov 9Nov 13Nov 18
16°FOct 27Nov 1Nov 5Nov 8Nov 12Nov 15Nov 18Nov 21Nov 25

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°F151146142138135131127122116
32°F169163160156152149145141134
28°F190183178175171166162157152
24°F210203198194190185181176169
20°F229220216213208204199195187
16°F248239234229225220216211203

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
7,441
Cooling degree days, base 65°F
802
Growing degree days, base 40°F
4,827
Growing degree days, base 45°F
3,780
Growing degree days, base 50°F
2,853
Growing degree days, base 55°F
2,048
Growing degree days, base 60°F
1,363

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,45200
February1,20101
March98809
April596156
May25927264
June50134535
July7297755
August13250702
September12489422
October5075103
November91708
December1,32800

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 9.8 km from Lower Brule. 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 USC00394766 (Lake Sharpe Prj). Public domain.