Sioux County climate

Sioux County Frost Dates and Growing Season

NOAA 1991-2020 normals for Mc Intosh 6 Se, 35.6 km from Sioux County, elevation 2179 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mc Intosh 6 Se. 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 9 and the first fall freeze around September 30, a growing season of about 143 days.

Median at 36°F
last May 18, first September 23
Median at 32°F
last May 9, first September 30
Median at 28°F
last April 30, 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 2May 29May 25May 22May 18May 15May 13May 10May 6
32°FMay 24May 17May 14May 11May 9May 6May 4May 1Apr 28
28°FMay 13May 8May 4May 2Apr 30Apr 27Apr 24Apr 19Apr 15
24°FMay 1Apr 28Apr 24Apr 21Apr 17Apr 15Apr 12Apr 9Apr 4
20°FApr 23Apr 18Apr 14Apr 11Apr 8Apr 6Apr 3Mar 31Mar 24
16°FApr 15Apr 10Apr 7Apr 4Apr 1Mar 29Mar 25Mar 20Mar 14

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 11Sep 15Sep 18Sep 21Sep 23Sep 25Sep 27Sep 29Oct 3
32°FSep 19Sep 23Sep 26Sep 28Sep 30Oct 2Oct 5Oct 8Oct 13
28°FSep 24Sep 29Oct 1Oct 5Oct 7Oct 10Oct 13Oct 17Oct 21
24°FOct 1Oct 6Oct 10Oct 14Oct 17Oct 20Oct 23Oct 26Oct 31
20°FOct 11Oct 16Oct 20Oct 24Oct 27Oct 29Nov 1Nov 4Nov 9
16°FOct 20Oct 26Oct 29Nov 1Nov 3Nov 6Nov 9Nov 13Nov 19

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°F142134131127124121117112106
32°F161155151147143139135131125
28°F182174169166161157153146140
24°F200194189184180176172167160
20°F220211206202198195191186179
16°F239231226220216212208202195

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
7,897
Cooling degree days, base 65°F
629
Growing degree days, base 40°F
4,469
Growing degree days, base 45°F
3,452
Growing degree days, base 50°F
2,558
Growing degree days, base 55°F
1,788
Growing degree days, base 60°F
1,140

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,50200
February1,24300
March1,01508
April612153
May29620231
June6996478
July13236688
August22209652
September16863359
October574484
November1,00205
December1,38100

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 35.6 km from Sioux 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 USC00395381 (Mc Intosh 6 Se). Public domain.