Ziebach County climate

Ziebach County Frost Dates and Growing Season

NOAA 1991-2020 normals for Dupree, 9 km from Ziebach County, elevation 2388 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dupree. 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 8 and the first fall freeze around October 1, a growing season of about 144 days.

Median at 36°F
last May 18, first September 24
Median at 32°F
last May 8, first October 1
Median at 28°F
last April 29, first October 9

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

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°F144139134131128124120115109
32°F164157152149144141136132124
28°F182175170166161158154149142
24°F202195190185181177171166159
20°F223214208204200195191186180
16°F241233226221217213207202194

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
7,122
Cooling degree days, base 65°F
900
Growing degree days, base 40°F
5,044
Growing degree days, base 45°F
3,963
Growing degree days, base 50°F
3,011
Growing degree days, base 55°F
2,186
Growing degree days, base 60°F
1,481

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,37600
February1,14501
March924017
April549379
May25533274
June46144550
July7323781
August12288741
September121102440
October5007119
November910011
December1,27900

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 km from Ziebach 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 USC00392429 (Dupree). Public domain.