Prineville climate

Prineville Frost Dates and Growing Season

NOAA 1991-2020 normals for Prineville, 0.5 km from Prineville, elevation 2876 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Prineville. 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 1 and the first fall freeze around September 22, a growing season of about 113 days.

Median at 36°F
last June 19, first September 4
Median at 32°F
last June 1, first September 22
Median at 28°F
last May 5, first October 8

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 8Jun 30Jun 25Jun 22Jun 19Jun 15Jun 11Jun 5May 31
32°FJun 22Jun 15Jun 10Jun 5Jun 1May 27May 21May 15May 8
28°FJun 1May 19May 13May 8May 5May 2Apr 29Apr 26Apr 19
24°FMay 6May 1Apr 27Apr 22Apr 18Apr 14Apr 11Apr 6Mar 30
20°FApr 18Apr 11Apr 5Apr 1Mar 29Mar 23Mar 16Mar 8Feb 25
16°FMar 31Mar 21Mar 12Mar 3Feb 26Feb 19Feb 12Feb 3Jan 15

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 15Aug 23Aug 29Sep 1Sep 4Sep 9Sep 12Sep 17Sep 23
32°FAug 31Sep 7Sep 12Sep 17Sep 22Sep 25Sep 30Oct 3Oct 9
28°FSep 18Sep 27Oct 1Oct 4Oct 8Oct 12Oct 16Oct 21Oct 27
24°FOct 5Oct 11Oct 16Oct 20Oct 24Oct 28Oct 31Nov 4Nov 14
20°FOct 18Oct 25Oct 29Nov 1Nov 4Nov 11Nov 17Nov 23Dec 1
16°FOct 29Nov 4Nov 11Nov 17Nov 23Nov 27Dec 1Dec 8Dec 18

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°F1039487837773676151
32°F1421321251191131071009383
28°F178169162156153148142133122
24°F216205198191186181175168159
20°F260246237230222217210202193
16°F314296285276270261251241227

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
5,992
Cooling degree days, base 65°F
323
Growing degree days, base 40°F
4,223
Growing degree days, base 45°F
3,027
Growing degree days, base 50°F
2,063
Growing degree days, base 55°F
1,302
Growing degree days, base 60°F
723

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January95601
February78402
March715010
April551045
May3369178
June17034319
July39132558
August48113530
September17235320
October476289
November752012
December99501

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 0.5 km from Prineville. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00356883 (Prineville). Public domain.