Eureka climate

Eureka Frost Dates and Growing Season

NOAA 1991-2020 normals for Eureka RS, 2.1 km from Eureka, elevation 2532 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Eureka RS. 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 11 and the first fall freeze around September 27, a growing season of about 138 days.

Median at 36°F
last May 26, first September 13
Median at 32°F
last May 11, first September 27
Median at 28°F
last April 28, first October 7

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

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°F1291231171131091041009587
32°F156150145141138134129124116
28°F188180173168164160156150143
24°F218210203198193188183177167
20°F248239232226220215210204195
16°F274263256251245240235228219

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
6,948
Cooling degree days, base 65°F
400
Growing degree days, base 40°F
4,127
Growing degree days, base 45°F
3,058
Growing degree days, base 50°F
2,158
Growing degree days, base 55°F
1,411
Growing degree days, base 60°F
821

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,21500
February98400
March82603
April546040
May29310206
June11946377
July27169607
August37148577
September19626291
October582054
November91802
December1,20600

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 2.1 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 USC00242827 (Eureka RS). Public domain.