Sioux County climate

Sioux County Frost Dates and Growing Season

NOAA 1991-2020 normals for Agate 3 E, 7.3 km from Sioux County, elevation 4670 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Agate 3 E. 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 30 and the first fall freeze around September 11, a growing season of about 103 days.

Median at 36°F
last June 14, first September 1
Median at 32°F
last May 30, first September 11
Median at 28°F
last May 17, first September 21

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°FJul 4Jun 28Jun 21Jun 17Jun 14Jun 10Jun 6Jun 2May 28
32°FJun 18Jun 11Jun 6Jun 2May 30May 27May 24May 20May 15
28°FJun 3May 28May 24May 20May 17May 14May 11May 8May 3
24°FMay 22May 16May 12May 9May 6May 3Apr 30Apr 27Apr 22
20°FMay 9May 4May 1Apr 28Apr 24Apr 20Apr 17Apr 13Apr 7
16°FApr 27Apr 22Apr 18Apr 15Apr 11Apr 8Apr 3Mar 31Mar 25

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°FAug 13Aug 21Aug 25Aug 29Sep 1Sep 3Sep 6Sep 10Sep 15
32°FAug 26Sep 1Sep 4Sep 8Sep 11Sep 14Sep 17Sep 21Sep 26
28°FSep 6Sep 11Sep 15Sep 18Sep 21Sep 25Sep 28Oct 2Oct 5
24°FSep 15Sep 21Sep 25Sep 29Oct 2Oct 4Oct 7Oct 10Oct 14
20°FSep 24Oct 1Oct 4Oct 8Oct 11Oct 13Oct 16Oct 19Oct 23
16°FOct 4Oct 10Oct 14Oct 18Oct 20Oct 22Oct 25Oct 29Nov 2

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°F1039488837872665949
32°F12611811210710398938779
28°F146139134130126122117111103
24°F166159154150146142138133127
20°F190183177172167163158152145
16°F211204198194189185180175167

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
7,065
Cooling degree days, base 65°F
493
Growing degree days, base 40°F
4,311
Growing degree days, base 45°F
3,250
Growing degree days, base 50°F
2,346
Growing degree days, base 55°F
1,588
Growing degree days, base 60°F
970

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,21700
February1,04100
March853010
April593046
May33311194
June8879443
July14206657
August26159598
September17737325
October566167
November92305
December1,23500

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 7.3 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 USC00250030 (Agate 3 E). Public domain.