Eureka climate

Eureka Frost Dates and Growing Season

NOAA 1991-2020 normals for Eureka 1E, 2.2 km from Eureka, elevation 1100 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Eureka 1E. 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 16 and the first fall freeze around October 20, a growing season of about 186 days.

Median at 36°F
last April 26, first October 12
Median at 32°F
last April 16, first October 20
Median at 28°F
last April 5, 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 8May 4May 1Apr 30Apr 26Apr 23Apr 20Apr 16Apr 12
32°FMay 1Apr 26Apr 22Apr 19Apr 16Apr 13Apr 9Apr 6Apr 1
28°FApr 21Apr 16Apr 12Apr 8Apr 5Apr 2Mar 31Mar 27Mar 20
24°FApr 10Apr 5Apr 1Mar 31Mar 27Mar 23Mar 19Mar 15Mar 9
20°FMar 31Mar 27Mar 22Mar 18Mar 15Mar 12Mar 8Mar 4Feb 27
16°FMar 22Mar 16Mar 12Mar 9Mar 5Mar 2Feb 28Feb 23Feb 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 28Oct 1Oct 5Oct 9Oct 12Oct 14Oct 17Oct 19Oct 23
32°FOct 5Oct 11Oct 15Oct 18Oct 20Oct 23Oct 26Oct 29Nov 2
28°FOct 16Oct 21Oct 24Oct 28Oct 30Nov 1Nov 4Nov 7Nov 13
24°FOct 24Oct 30Nov 1Nov 5Nov 7Nov 10Nov 14Nov 19Nov 25
20°FNov 1Nov 6Nov 9Nov 12Nov 17Nov 20Nov 24Nov 30Dec 4
16°FNov 8Nov 14Nov 19Nov 23Nov 28Dec 1Dec 4Dec 9Dec 16

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°F184178174170167163160156150
32°F205198193190186182178173166
28°F227218213210206201197192186
24°F249242236230225221216211203
20°F271262257252247242236230222
16°F292283277272268263258251244

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
4,890
Cooling degree days, base 65°F
1,392
Growing degree days, base 40°F
6,551
Growing degree days, base 45°F
5,245
Growing degree days, base 50°F
4,078
Growing degree days, base 55°F
3,049
Growing degree days, base 60°F
2,154

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,06303
February841012
March627369
April32915196
May10989448
June7272715
July0426891
August1381845
September48173577
October27930259
November622156
December96406

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 2.2 km from Eureka. 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 USC00142622 (Eureka 1E). Public domain.