Owyhee County climate

Owyhee County Frost Dates and Growing Season

NOAA 1991-2020 normals for Bruneau, 44.9 km from Owyhee County, elevation 2530 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bruneau. 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 April 17 and the first fall freeze around October 17, a growing season of about 181 days.

Median at 36°F
last May 3, first October 3
Median at 32°F
last April 17, first October 17
Median at 28°F
last March 30, first October 31

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 19May 14May 10May 7May 3Apr 30Apr 28Apr 24Apr 18
32°FMay 7May 1Apr 26Apr 22Apr 17Apr 14Apr 10Apr 5Mar 31
28°FApr 18Apr 11Apr 6Apr 2Mar 30Mar 26Mar 20Mar 15Mar 9
24°FMar 28Mar 19Mar 14Mar 9Mar 6Mar 2Feb 27Feb 23Feb 15
20°FMar 7Mar 2Feb 27Feb 23Feb 20Feb 15Feb 10Feb 5Jan 23
16°FFeb 25Feb 18Feb 13Feb 7Feb 2Jan 27Jan 15Jan 4Dec 24

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

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°F172166161156151147143137130
32°F203195190185181177173166157
28°F241231224218213209203197187
24°F273264258252247242237231222
20°F307296289281275270264257248
16°F345331321313306299291282271

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
97% 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
4,669
Cooling degree days, base 65°F
1,127
Growing degree days, base 40°F
6,120
Growing degree days, base 45°F
4,755
Growing degree days, base 50°F
3,580
Growing degree days, base 55°F
2,592
Growing degree days, base 60°F
1,780

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January92801
February69905
March530053
April3285157
May15257374
June31179599
July1409872
August4354815
September67114499
October3328178
November660024
December93903

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 44.9 km from Owyhee 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 USC00101195 (Bruneau). Public domain.