Granite Falls climate

Granite Falls Frost Dates and Growing Season

NOAA 1991-2020 normals for Granite Falls, 0.6 km from Granite Falls, elevation 930 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Granite Falls. 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 4 and the first fall freeze around October 1, a growing season of about 150 days.

Median at 36°F
last May 15, first September 22
Median at 32°F
last May 4, first October 1
Median at 28°F
last April 25, first October 11

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°FMay 30May 24May 21May 17May 15May 12May 9May 6May 1
32°FMay 18May 13May 10May 7May 4May 2Apr 30Apr 27Apr 21
28°FMay 9May 4May 1Apr 28Apr 25Apr 22Apr 18Apr 15Apr 9
24°FApr 30Apr 25Apr 21Apr 17Apr 14Apr 12Apr 8Apr 6Apr 2
20°FApr 22Apr 16Apr 12Apr 9Apr 6Apr 4Apr 2Mar 30Mar 23
16°FApr 14Apr 8Apr 5Apr 3Mar 31Mar 29Mar 24Mar 20Mar 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°FSep 9Sep 14Sep 17Sep 20Sep 22Sep 25Sep 29Oct 2Oct 6
32°FSep 17Sep 21Sep 25Sep 28Oct 1Oct 4Oct 7Oct 10Oct 15
28°FSep 26Sep 30Oct 4Oct 8Oct 11Oct 15Oct 18Oct 21Oct 25
24°FOct 5Oct 12Oct 17Oct 20Oct 23Oct 26Oct 29Nov 1Nov 6
20°FOct 19Oct 24Oct 27Oct 30Nov 1Nov 4Nov 7Nov 10Nov 15
16°FOct 28Nov 1Nov 4Nov 7Nov 10Nov 12Nov 15Nov 18Nov 22

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°F148142138133129126122117111
32°F168161157153150146142137129
28°F188182177172168164160155147
24°F210203198194189185181175168
20°F229222216212208204200195188
16°F245237232228224220216211203

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
8,003
Cooling degree days, base 65°F
629
Growing degree days, base 40°F
4,562
Growing degree days, base 45°F
3,545
Growing degree days, base 50°F
2,634
Growing degree days, base 55°F
1,841
Growing degree days, base 60°F
1,170

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,59900
February1,32100
March1,05909
April598265
May25033272
June44126533
July7236694
August21167610
September16460355
October546589
November97406
December1,42100

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 0.6 km from Granite Falls. 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 USC00213311 (Granite Falls). Public domain.