Wallowa County climate

Wallowa County Frost Dates and Growing Season

NOAA 1991-2020 normals for Enterprise 20 Nne, 14.4 km from Wallowa County, elevation 3280 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Enterprise 20 Nne. 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 June 8 and the first fall freeze around September 5, a growing season of about 84 days.

Median at 32°F
last June 8, first September 5
Median at 28°F
last May 13, first September 22

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°F–––––––––
32°FJul 8Jun 30Jun 20Jun 14Jun 8Jun 3May 30May 24May 18
28°FJun 5May 28May 21May 17May 13May 10May 7May 2Apr 28
24°FMay 11May 5May 1Apr 29Apr 26Apr 22Apr 18Apr 14Apr 7
20°FApr 28Apr 21Apr 17Apr 12Apr 8Apr 3Mar 30Mar 21Mar 11
16°FApr 5Mar 30Mar 24Mar 17Mar 12Mar 8Mar 3Feb 28Feb 22

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°F–––––––––
32°FAug 16Aug 24Aug 30Sep 2Sep 5Sep 9Sep 13Sep 16Sep 22
28°FSep 3Sep 10Sep 15Sep 18Sep 22Sep 25Sep 28Oct 2Oct 9
24°FSep 17Sep 23Sep 28Oct 1Oct 5Oct 9Oct 15Oct 21Oct 30
20°FOct 1Oct 6Oct 12Oct 18Oct 23Oct 28Nov 1Nov 6Nov 14
16°FOct 12Oct 21Oct 27Nov 1Nov 5Nov 11Nov 15Nov 21Nov 27

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°F736458524642363226
32°F11510597918479726556
28°F152144138131126122116109100
24°F188180173167161156151145135
20°F232219209202195190183177167
16°F268257249242236230222215203

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
7,116
Cooling degree days, base 65°F
248
Growing degree days, base 40°F
3,622
Growing degree days, base 45°F
2,591
Growing degree days, base 50°F
1,750
Growing degree days, base 55°F
1,082
Growing degree days, base 60°F
575

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,15600
February90700
March82302
April624023
May3945133
June20023281
July61109513
August5895503
September23417249
October581045
November90202
December1,17600

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 14.4 km from Wallowa 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 USC00352678 (Enterprise 20 Nne). Public domain.