Pierce County climate

Pierce County Frost Dates and Growing Season

NOAA 1991-2020 normals for Ellsworth 1E, 3.1 km from Pierce County, elevation 1030 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ellsworth 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 May 13 and the first fall freeze around September 29, a growing season of about 139 days.

Median at 36°F
last May 23, first September 20
Median at 32°F
last May 13, first September 29
Median at 28°F
last May 2, first October 8

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 3May 31May 28May 26May 23May 20May 17May 13May 8
32°FMay 27May 22May 19May 16May 13May 10May 7May 3Apr 29
28°FMay 17May 12May 8May 5May 2Apr 30Apr 27Apr 23Apr 19
24°FMay 7May 2Apr 28Apr 25Apr 22Apr 18Apr 15Apr 11Apr 6
20°FApr 26Apr 20Apr 17Apr 13Apr 10Apr 7Apr 4Apr 2Mar 28
16°FApr 17Apr 10Apr 6Apr 4Apr 2Mar 31Mar 28Mar 24Mar 17

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 6Sep 12Sep 15Sep 18Sep 20Sep 23Sep 27Oct 1Oct 4
32°FSep 15Sep 20Sep 24Sep 27Sep 29Oct 2Oct 5Oct 7Oct 11
28°FSep 25Sep 30Oct 3Oct 5Oct 8Oct 11Oct 13Oct 17Oct 22
24°FOct 4Oct 8Oct 12Oct 15Oct 18Oct 20Oct 24Oct 27Nov 1
20°FOct 15Oct 19Oct 23Oct 26Oct 29Oct 31Nov 2Nov 5Nov 10
16°FOct 25Oct 30Nov 1Nov 3Nov 5Nov 8Nov 11Nov 15Nov 20

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°F140133129125122118113108101
32°F159151147143139136132126121
28°F176171166162159154150144139
24°F198192187183179175170165158
20°F217212206202199195191186179
16°F235229224220217213208204198

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
8,581
Cooling degree days, base 65°F
347
Growing degree days, base 40°F
3,921
Growing degree days, base 45°F
2,956
Growing degree days, base 50°F
2,109
Growing degree days, base 55°F
1,381
Growing degree days, base 60°F
781

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,64800
February1,36200
March1,11906
April676139
May33416196
June8671436
July29134570
August5190504
September21332288
October598365
November1,01704
December1,44800

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 3.1 km from Pierce County. 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 USC00472556 (Ellsworth 1E). Public domain.