Grangeville climate

Grangeville Frost Dates and Growing Season

NOAA 1991-2020 normals for Grangeville, 1.6 km from Grangeville, elevation 3300 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Grangeville. 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 9 and the first fall freeze around October 3, a growing season of about 146 days.

Median at 36°F
last May 28, first September 19
Median at 32°F
last May 9, first October 3
Median at 28°F
last April 22, first October 15

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 16Jun 10Jun 4Jun 1May 28May 24May 20May 15May 10
32°FMay 27May 20May 15May 11May 9May 5May 2Apr 29Apr 24
28°FMay 8May 3Apr 29Apr 26Apr 22Apr 18Apr 14Apr 10Apr 4
24°FApr 25Apr 15Apr 10Apr 6Apr 2Mar 30Mar 25Mar 20Mar 13
20°FApr 3Mar 27Mar 22Mar 17Mar 13Mar 10Mar 6Mar 2Feb 25
16°FMar 15Mar 10Mar 5Mar 2Feb 28Feb 24Feb 18Feb 13Feb 3

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 4Sep 9Sep 13Sep 16Sep 19Sep 23Sep 26Oct 1Oct 6
32°FSep 14Sep 21Sep 26Sep 30Oct 3Oct 6Oct 9Oct 12Oct 17
28°FSep 29Oct 5Oct 8Oct 12Oct 15Oct 18Oct 22Oct 26Nov 1
24°FOct 11Oct 17Oct 21Oct 25Oct 29Nov 1Nov 5Nov 11Nov 17
20°FOct 20Oct 29Nov 2Nov 7Nov 11Nov 14Nov 20Nov 24Nov 30
16°FOct 31Nov 8Nov 13Nov 19Nov 23Nov 26Nov 30Dec 5Dec 12

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°F1381281221171121071039790
32°F167160155151146141136129119
28°F200192186180176171166160153
24°F237228221215209204198191181
20°F269261253246241235229221212
16°F303292284277270264257249239

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
6,675
Cooling degree days, base 65°F
313
Growing degree days, base 40°F
3,831
Growing degree days, base 45°F
2,755
Growing degree days, base 50°F
1,888
Growing degree days, base 55°F
1,200
Growing degree days, base 60°F
677

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,04900
February87600
March79503
April597031
May3854137
June20219274
July44133555
August46130549
September21027281
October557054
November84004
December1,07400

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 1.6 km from Grangeville. 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 USC00103771 (Grangeville). Public domain.