Roberts County climate

Roberts County Frost Dates and Growing Season

NOAA 1991-2020 normals for Sisseton Muni AP, 5.6 km from Roberts County, elevation 1161 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Sisseton Muni AP. 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 3 and the first fall freeze around September 30, a growing season of about 149 days.

Median at 36°F
last May 14, first September 22
Median at 32°F
last May 3, first September 30
Median at 28°F
last April 24, first October 10

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 27May 22May 19May 16May 14May 11May 8May 5Apr 30
32°FMay 16May 13May 9May 6May 3May 1Apr 29Apr 26Apr 21
28°FMay 8May 3Apr 30Apr 27Apr 24Apr 21Apr 18Apr 14Apr 10
24°FApr 29Apr 24Apr 21Apr 18Apr 15Apr 12Apr 9Apr 6Apr 3
20°FApr 21Apr 16Apr 12Apr 9Apr 7Apr 4Apr 2Mar 29Mar 22
16°FApr 13Apr 9Apr 5Apr 3Mar 31Mar 27Mar 23Mar 18Mar 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 9Sep 13Sep 16Sep 19Sep 22Sep 24Sep 27Sep 29Oct 3
32°FSep 17Sep 22Sep 25Sep 28Sep 30Oct 3Oct 5Oct 9Oct 13
28°FSep 26Oct 1Oct 4Oct 7Oct 10Oct 13Oct 17Oct 21Oct 25
24°FOct 6Oct 11Oct 16Oct 20Oct 22Oct 25Oct 28Oct 31Nov 4
20°FOct 16Oct 23Oct 27Oct 30Nov 1Nov 3Nov 6Nov 10Nov 17
16°FOct 27Nov 1Nov 4Nov 7Nov 10Nov 13Nov 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°F148142137133130126122118112
32°F167161156151149145141136131
28°F187180176172168164160154147
24°F208201196192188184180175167
20°F228220215210206202198192185
16°F244237232227223218213209202

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
8,179
Cooling degree days, base 65°F
566
Growing degree days, base 40°F
4,392
Growing degree days, base 45°F
3,392
Growing degree days, base 50°F
2,501
Growing degree days, base 55°F
1,726
Growing degree days, base 60°F
1,077

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,60100
February1,32700
March1,08706
April638148
May27030258
June52118516
July11211665
August28149586
September18053335
October571581
November99206
December1,42300

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 5.6 km from Roberts County. 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 USW00094993 (Sisseton Muni AP). Public domain.