Pateros climate

Pateros Frost Dates and Growing Season

NOAA 1991-2020 normals for Chief Joseph Dam, 19.9 km from Pateros, elevation 834 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chief Joseph Dam. 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 26 and the first fall freeze around October 11, a growing season of about 167 days.

Median at 36°F
last May 10, first October 1
Median at 32°F
last April 26, first October 11
Median at 28°F
last April 9, first October 23

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°FJun 1May 23May 18May 13May 10May 7May 3Apr 30Apr 26
32°FMay 13May 7May 2Apr 30Apr 26Apr 23Apr 19Apr 14Apr 9
28°FMay 2Apr 24Apr 18Apr 13Apr 9Apr 4Mar 31Mar 26Mar 17
24°FApr 19Apr 5Mar 30Mar 24Mar 17Mar 13Mar 9Mar 6Mar 1
20°FMar 24Mar 15Mar 9Mar 5Mar 1Feb 27Feb 23Feb 18Feb 10
16°FMar 10Mar 4Feb 28Feb 24Feb 19Feb 13Feb 7Feb 1Jan 21

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 27Sep 29Oct 1Oct 3Oct 6Oct 10Oct 15
32°FSep 30Oct 3Oct 5Oct 8Oct 11Oct 15Oct 18Oct 21Oct 27
28°FOct 7Oct 12Oct 17Oct 20Oct 23Oct 26Oct 30Nov 1Nov 6
24°FOct 18Oct 24Oct 28Oct 31Nov 3Nov 7Nov 11Nov 16Nov 22
20°FOct 27Nov 1Nov 6Nov 11Nov 15Nov 19Nov 23Nov 28Dec 5
16°FNov 4Nov 13Nov 19Nov 23Nov 27Dec 1Dec 7Dec 16Dec 26

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°F163156151146142138132126117
32°F190182177172167163159154147
28°F223214207201196190185177167
24°F257247241235230225218209197
20°F289276270265258253247240229
16°F319307298290284279273265255

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
5,874
Cooling degree days, base 65°F
794
Growing degree days, base 40°F
5,148
Growing degree days, base 45°F
3,966
Growing degree days, base 50°F
2,942
Growing degree days, base 55°F
2,077
Growing degree days, base 60°F
1,359

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,13100
February88900
March687011
April418186
May18828311
June5798491
July8305762
August7284742
September9277436
October453299
November82703
December1,11900

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 19.9 km from Pateros. 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 USC00451400 (Chief Joseph Dam). Public domain.