Pierce County climate

Pierce County Frost Dates and Growing Season

NOAA 1991-2020 normals for Rugby, 11.7 km from Pierce County, elevation 1550 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Rugby. 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 17 and the first fall freeze around September 23, a growing season of about 129 days.

Median at 36°F
last May 26, first September 14
Median at 32°F
last May 17, first September 23
Median at 28°F
last May 6, first October 1

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

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 31Sep 4Sep 8Sep 11Sep 14Sep 17Sep 19Sep 22Sep 25
32°FSep 11Sep 15Sep 18Sep 21Sep 23Sep 25Sep 28Oct 1Oct 5
28°FSep 20Sep 24Sep 27Sep 29Oct 1Oct 4Oct 6Oct 9Oct 14
24°FSep 28Oct 1Oct 4Oct 7Oct 10Oct 13Oct 16Oct 20Oct 24
20°FOct 5Oct 10Oct 14Oct 17Oct 21Oct 24Oct 27Oct 30Nov 2
16°FOct 12Oct 19Oct 23Oct 27Oct 29Nov 1Nov 3Nov 6Nov 11

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°F127120116112108104999384
32°F146141136132129125121116109
28°F165158154150147143140135129
24°F186179174169166161158153147
20°F204198194189185181177170163
16°F221213209205201197193187182

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
9,801
Cooling degree days, base 65°F
304
Growing degree days, base 40°F
3,594
Growing degree days, base 45°F
2,699
Growing degree days, base 50°F
1,910
Growing degree days, base 55°F
1,236
Growing degree days, base 60°F
691

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,82900
February1,52500
March1,28001
April752026
May37711170
June11350390
July39116542
August62103507
September27222233
October717140
November1,19101
December1,64400

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 11.7 km from Pierce County. 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 USC00327704 (Rugby). Public domain.