Nezperce climate

Nezperce Frost Dates and Growing Season

NOAA 1991-2020 normals for Nezperce, 0.3 km from Nezperce, elevation 3248 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Nezperce. 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 24 and the first fall freeze around September 20, a growing season of about 116 days.

Median at 32°F
last May 24, first September 20
Median at 28°F
last May 5, first October 2

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°FJun 19Jun 10Jun 3May 29May 24May 20May 16May 12May 6
28°FMay 25May 17May 12May 9May 5May 3Apr 30Apr 26Apr 19
24°FMay 8May 2Apr 27Apr 22Apr 16Apr 10Apr 5Mar 30Mar 22
20°FApr 16Apr 5Mar 31Mar 26Mar 21Mar 15Mar 10Mar 6Feb 28
16°FMar 26Mar 17Mar 12Mar 7Mar 3Feb 28Feb 23Feb 17Feb 8

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°FSep 1Sep 7Sep 12Sep 16Sep 20Sep 23Sep 26Sep 30Oct 5
28°FSep 13Sep 21Sep 25Sep 29Oct 2Oct 5Oct 8Oct 13Oct 19
24°FSep 28Oct 2Oct 7Oct 12Oct 16Oct 21Oct 25Oct 30Nov 5
20°FOct 10Oct 18Oct 24Oct 29Nov 2Nov 8Nov 13Nov 19Nov 25
16°FOct 22Oct 31Nov 6Nov 12Nov 17Nov 21Nov 25Nov 29Dec 8

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°F988983757063565043
32°F1411331271211161111059586
28°F174165159154149143138131122
24°F217206198191186180172164155
20°F256247239231226219211203192
16°F293281273266259252245238226

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
7,448
Cooling degree days, base 65°F
148
Growing degree days, base 40°F
3,212
Growing degree days, base 45°F
2,227
Growing degree days, base 50°F
1,443
Growing degree days, base 55°F
835
Growing degree days, base 60°F
405

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,12800
February93100
March86001
April657017
May448199
June2779199
July9760429
August9164440
September27113218
October620039
November90602
December1,16100

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 0.3 km from Nezperce. 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 USC00106424 (Nezperce). Public domain.