Yelm climate

Yelm Frost Dates and Growing Season

NOAA 1991-2020 normals for Olympia AP, 22.8 km from Yelm, elevation 188 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Olympia AP. 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 29 and the first fall freeze around October 14, a growing season of about 169 days.

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

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 12Sep 17Sep 22Sep 25Sep 28Oct 1Oct 5Oct 9Oct 14
32°FSep 28Oct 3Oct 6Oct 10Oct 14Oct 18Oct 21Oct 26Nov 1
28°FOct 9Oct 19Oct 24Oct 28Nov 1Nov 5Nov 10Nov 15Nov 24
24°FOct 28Nov 2Nov 9Nov 14Nov 20Nov 25Dec 1Dec 7Dec 21
20°FNov 6Nov 15Nov 23Nov 30Dec 6Dec 14Dec 26Jan 2Jan 29
16°FNov 15Nov 27Dec 4Dec 11Dec 18Dec 28Jan 5Jan 26Feb 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°F158150145140135131126120113
32°F195186181175169164159152144
28°F239230223216210205198191181
24°F303288276268261253246237225
20°F352335327318311302292280266
16°F365365365358345334325316305

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
96% of years
16°F or colder
68% 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
5,378
Cooling degree days, base 65°F
113
Growing degree days, base 40°F
4,138
Growing degree days, base 45°F
2,773
Growing degree days, base 50°F
1,723
Growing degree days, base 55°F
936
Growing degree days, base 60°F
397

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January78702
February68002
March64809
April504039
May3262159
June18912274
July7347439
August6744442
September1838276
October454071
November654011
December81102

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 22.8 km from Yelm. 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 USW00024227 (Olympia AP). Public domain.