Ellsworth climate

Ellsworth Frost Dates and Growing Season

NOAA 1991-2020 normals for Ellsworth, 0.3 km from Ellsworth, elevation 1568 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ellsworth. 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 16, a growing season of about 175 days.

Median at 36°F
last May 1, first October 7
Median at 32°F
last April 23, first October 16
Median at 28°F
last April 13, first October 26

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 13May 9May 6May 3May 1Apr 29Apr 26Apr 23Apr 18
32°FMay 5May 1Apr 28Apr 26Apr 23Apr 20Apr 17Apr 14Apr 10
28°FApr 27Apr 22Apr 19Apr 16Apr 13Apr 10Apr 7Apr 3Mar 29
24°FApr 18Apr 12Apr 8Apr 5Apr 2Mar 31Mar 27Mar 22Mar 15
20°FApr 9Apr 3Mar 31Mar 26Mar 22Mar 18Mar 14Mar 10Mar 4
16°FApr 3Mar 26Mar 20Mar 15Mar 11Mar 7Mar 4Feb 28Feb 23

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 24Sep 29Oct 1Oct 5Oct 7Oct 10Oct 13Oct 16Oct 20
32°FSep 30Oct 5Oct 10Oct 13Oct 16Oct 18Oct 22Oct 25Oct 29
28°FOct 9Oct 16Oct 20Oct 23Oct 26Oct 28Oct 31Nov 3Nov 8
24°FOct 20Oct 25Oct 29Nov 1Nov 3Nov 6Nov 9Nov 12Nov 18
20°FOct 28Nov 1Nov 5Nov 8Nov 11Nov 15Nov 18Nov 23Dec 1
16°FNov 3Nov 9Nov 14Nov 17Nov 21Nov 25Nov 30Dec 3Dec 9

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°F175169165161158155151146140
32°F193187183178175171167162155
28°F214207203199195191187182175
24°F235227222217214210206201194
20°F259251244238233229223218210
16°F277270263258252247241236226

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
5,207
Cooling degree days, base 65°F
1,507
Growing degree days, base 40°F
6,484
Growing degree days, base 45°F
5,219
Growing degree days, base 50°F
4,097
Growing degree days, base 55°F
3,107
Growing degree days, base 60°F
2,241

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,09001
February883010
March668258
April36716174
May128103447
June9311751
July1467931
August2394857
September61184575
October30930245
November669146
December1,02101

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 0.3 km from Ellsworth. 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 USC00142459 (Ellsworth). Public domain.