Eureka climate

Eureka Frost Dates and Growing Season

NOAA 1991-2020 normals for Eureka, 0.4 km from Eureka, elevation 6430 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Eureka. 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 June 2 and the first fall freeze around September 29, a growing season of about 119 days.

Median at 36°F
last June 13, first September 19
Median at 32°F
last June 2, first September 29
Median at 28°F
last May 15, first October 10

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 28Jun 24Jun 20Jun 16Jun 13Jun 10Jun 7Jun 3May 31
32°FJun 19Jun 13Jun 8Jun 5Jun 2May 30May 25May 20May 13
28°FJun 5May 31May 25May 19May 15May 11May 6May 2Apr 27
24°FMay 18May 12May 7May 3Apr 30Apr 27Apr 23Apr 19Apr 11
20°FMay 3Apr 28Apr 23Apr 19Apr 14Apr 10Apr 6Apr 2Mar 26
16°FApr 19Apr 10Apr 5Apr 2Mar 30Mar 24Mar 17Mar 11Mar 4

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 21Sep 24Sep 26Sep 30
32°FSep 16Sep 21Sep 25Sep 27Sep 29Oct 1Oct 4Oct 8Oct 13
28°FSep 27Oct 1Oct 3Oct 7Oct 10Oct 13Oct 16Oct 20Oct 24
24°FOct 5Oct 9Oct 13Oct 17Oct 20Oct 23Oct 26Oct 29Nov 4
20°FOct 13Oct 19Oct 23Oct 27Oct 30Nov 1Nov 5Nov 9Nov 16
16°FOct 22Oct 28Nov 1Nov 5Nov 9Nov 13Nov 18Nov 21Nov 27

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°F1151091041019693888376
32°F14313412812311911511010598
28°F169161156151146142136129122
24°F194187182177173168163156148
20°F222213206201196190185180171
16°F253244236230225219213207198

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
7,155
Cooling degree days, base 65°F
334
Growing degree days, base 40°F
3,875
Growing degree days, base 45°F
2,866
Growing degree days, base 50°F
2,021
Growing degree days, base 55°F
1,327
Growing degree days, base 60°F
762

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,15300
February98700
March88804
April698021
May4513119
June16733331
July18154601
August25124564
September18820302
October543073
November87006
December1,16900

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 0.4 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 USC00262708 (Eureka). Public domain.