Eureka climate

Eureka Frost Dates and Growing Season

NOAA 1991-2020 normals for Eureka, 0.4 km from Eureka, elevation 1871 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 May 12 and the first fall freeze around September 27, a growing season of about 137 days.

Median at 36°F
last May 22, first September 19
Median at 32°F
last May 12, first September 27
Median at 28°F
last May 2, first October 4

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 5May 31May 28May 25May 22May 20May 17May 14May 10
32°FMay 25May 21May 18May 15May 12May 9May 7May 4May 1
28°FMay 16May 11May 8May 5May 2Apr 30Apr 28Apr 24Apr 19
24°FMay 7May 2Apr 30Apr 28Apr 24Apr 21Apr 18Apr 15Apr 10
20°FApr 29Apr 25Apr 21Apr 17Apr 15Apr 12Apr 9Apr 6Apr 1
16°FApr 22Apr 16Apr 12Apr 9Apr 7Apr 4Apr 1Mar 28Mar 21

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

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°F135130125122119115111106100
32°F153148144140137134130125119
28°F172166162157154151146142135
24°F190184179175172168164158152
20°F209202198194190186181176169
16°F228220215211207203199193187

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
8,874
Cooling degree days, base 65°F
447
Growing degree days, base 40°F
3,966
Growing degree days, base 45°F
3,023
Growing degree days, base 50°F
2,192
Growing degree days, base 55°F
1,481
Growing degree days, base 60°F
893

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,66900
February1,39200
March1,15003
April692134
May34114193
June9073435
July24178618
August41144567
September22138289
October662251
November1,09201
December1,50000

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.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00392797 (Eureka). Public domain.