Pierce climate

Pierce Frost Dates and Growing Season

NOAA 1991-2020 normals for Nunn 7 Nne, 19 km from Pierce, elevation 5390 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Nunn 7 Nne. 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 27, a growing season of about 136 days.

Median at 36°F
last May 25, first September 19
Median at 32°F
last May 13, first September 27
Median at 28°F
last May 4, 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 6Jun 2May 31May 28May 25May 23May 20May 17May 12
32°FMay 27May 21May 18May 16May 13May 11May 9May 6May 2
28°FMay 16May 12May 8May 6May 4May 1Apr 29Apr 27Apr 22
24°FMay 7May 3Apr 30Apr 28Apr 25Apr 22Apr 19Apr 15Apr 10
20°FApr 30Apr 25Apr 20Apr 17Apr 13Apr 10Apr 7Apr 3Mar 31
16°FApr 19Apr 13Apr 8Apr 5Apr 2Mar 30Mar 26Mar 22Mar 14

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 10Sep 14Sep 17Sep 19Sep 22Sep 24Sep 26Sep 30
32°FSep 14Sep 19Sep 23Sep 25Sep 27Sep 29Oct 2Oct 5Oct 9
28°FSep 24Sep 28Oct 1Oct 4Oct 7Oct 10Oct 12Oct 16Oct 19
24°FOct 3Oct 7Oct 10Oct 13Oct 16Oct 18Oct 22Oct 25Oct 28
20°FOct 11Oct 16Oct 18Oct 22Oct 25Oct 27Oct 31Nov 2Nov 8
16°FOct 18Oct 23Oct 26Oct 30Nov 2Nov 5Nov 8Nov 11Nov 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°F13212712412011711310910398
32°F153147143139136132128123118
28°F174168163159156152148144137
24°F192187182178174170166161154
20°F213207202198194189185179172
16°F237227223218213207202196189

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
6,845
Cooling degree days, base 65°F
434
Growing degree days, base 40°F
4,268
Growing degree days, base 45°F
3,191
Growing degree days, base 50°F
2,280
Growing degree days, base 55°F
1,521
Growing degree days, base 60°F
904

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,15001
February99301
March84009
April612036
May3456182
June9161421
July10182636
August26149587
September17635323
October555177
November88106
December1,16500

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 19 km from Pierce. 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 USW00094074 (Nunn 7 Nne). Public domain.