Cottage Grove climate

Cottage Grove Frost Dates and Growing Season

NOAA 1991-2020 normals for Hastings Dam 2, 9.6 km from Cottage Grove, elevation 680 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hastings Dam 2. 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 23 and the first fall freeze around October 19, a growing season of about 177 days.

Median at 36°F
last May 4, first October 8
Median at 32°F
last April 23, first October 19
Median at 28°F
last April 11, first October 30

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

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 26Sep 30Oct 3Oct 6Oct 8Oct 11Oct 14Oct 18Oct 22
32°FOct 5Oct 10Oct 13Oct 16Oct 19Oct 22Oct 25Oct 28Nov 1
28°FOct 14Oct 20Oct 24Oct 27Oct 30Nov 1Nov 3Nov 7Nov 12
24°FOct 25Oct 31Nov 1Nov 4Nov 7Nov 10Nov 13Nov 16Nov 20
20°FNov 1Nov 6Nov 10Nov 12Nov 15Nov 18Nov 20Nov 23Nov 28
16°FNov 8Nov 14Nov 17Nov 20Nov 22Nov 25Nov 28Dec 1Dec 6

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°F176169164160156152148144138
32°F197190185181177174169164157
28°F216210205202198194189184178
24°F236227223219215212208203196
20°F249242237234230226222218212
16°F263256251247243239235231224

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
7,613
Cooling degree days, base 65°F
726
Growing degree days, base 40°F
4,780
Growing degree days, base 45°F
3,742
Growing degree days, base 50°F
2,809
Growing degree days, base 55°F
1,992
Growing degree days, base 60°F
1,295

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,55300
February1,29200
March1,04009
April570266
May24332275
June40151561
July6258718
August11200654
September12775403
October4827113
November906011
December1,34200

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 9.6 km from Cottage Grove. 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 USC00213567 (Hastings Dam 2). Public domain.