Tahoma climate

Tahoma Frost Dates and Growing Season

NOAA 1991-2020 normals for Tahoma, 0.8 km from Tahoma, elevation 6315 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Tahoma. 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 June 4 and the first fall freeze around October 3, a growing season of about 120 days.

Median at 32°F
last June 4, first October 3
Median at 28°F
last May 15, first October 16

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°F–––––––––
32°FJun 20Jun 13Jun 10Jun 7Jun 4Jun 1May 29May 24May 19
28°FJun 4May 28May 24May 20May 15May 11May 7May 3Apr 29
24°FMay 17May 10May 5May 1Apr 28Apr 24Apr 21Apr 18Apr 11
20°FMay 2Apr 25Apr 20Apr 16Apr 12Apr 8Apr 5Mar 31Mar 19
16°FApr 15Apr 8Apr 3Mar 27Mar 19Mar 12Mar 6Mar 1Feb 20

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°F–––––––––
32°FSep 17Sep 23Sep 27Oct 1Oct 3Oct 6Oct 9Oct 12Oct 16
28°FOct 2Oct 7Oct 11Oct 13Oct 16Oct 20Oct 23Oct 29Nov 2
24°FOct 14Oct 19Oct 24Oct 29Nov 1Nov 4Nov 7Nov 12Nov 18
20°FOct 26Nov 3Nov 9Nov 14Nov 18Nov 22Nov 25Nov 30Dec 5
16°FNov 15Nov 22Nov 26Nov 30Dec 2Dec 5Dec 10Dec 16Dec 22

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°F1079993888277716454
32°F14113412812412011611110696
28°F179169163158153148143137129
24°F207200195191187182177170161
20°F246236229223217211206199190
16°F296282273265257250242235223

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
7,907
Cooling degree days, base 65°F
27
Growing degree days, base 40°F
2,694
Growing degree days, base 45°F
1,806
Growing degree days, base 50°F
1,108
Growing degree days, base 55°F
552
Growing degree days, base 60°F
179

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,09400
February98700
March96700
April81200
May598029
June3182166
July12617357
August1337339
September2911186
October598031
November87800
December1,10500

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 0.8 km from Tahoma. 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 USC00048760 (Tahoma). Public domain.