Maple Valley climate

Maple Valley Frost Dates and Growing Season

NOAA 1991-2020 normals for Landsburg, 6.6 km from Maple Valley, elevation 535 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Landsburg. 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 20 and the first fall freeze around October 25, a growing season of about 187 days.

Median at 36°F
last May 10, first October 6
Median at 32°F
last April 20, first October 25
Median at 28°F
last March 24, first November 12

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 7May 27May 20May 15May 10May 6May 2Apr 29Apr 23
32°FMay 10May 4Apr 29Apr 25Apr 20Apr 16Apr 12Apr 6Mar 31
28°FApr 16Apr 7Apr 2Mar 29Mar 24Mar 19Mar 14Mar 7Feb 28
24°FMar 18Mar 10Mar 4Feb 28Feb 22Feb 16Feb 5Jan 22Jan 3
20°FFeb 28Feb 21Feb 13Feb 1Jan 20Jan 6Dec 30Dec 16Dec 4
16°FFeb 11Jan 22Jan 6Jan 1Dec 30Dec 24Dec 15Dec 9Dec 1

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 19Sep 27Oct 1Oct 3Oct 6Oct 9Oct 14Oct 18Oct 26
32°FOct 5Oct 13Oct 17Oct 21Oct 25Oct 29Nov 1Nov 6Nov 12
28°FOct 24Oct 31Nov 3Nov 8Nov 12Nov 17Nov 23Nov 30Dec 8
24°FNov 8Nov 14Nov 21Nov 26Dec 1Dec 7Dec 13Dec 21Jan 3
20°FNov 17Nov 28Dec 3Dec 11Dec 18Dec 26Jan 1Jan 14Feb 6
16°FNov 25Dec 2Dec 10Dec 14Dec 22Dec 28Jan 1Jan 9Feb 2

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°F174165160153146141134126111
32°F215205199193187181177170160
28°F267256248240233226221213202
24°F335319306296288279270259246
20°F365365356345335327318307293
16°F365365365365365365355341326

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
98% of years
20°F or colder
77% of years
16°F or colder
34% 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
5,407
Cooling degree days, base 65°F
130
Growing degree days, base 40°F
4,124
Growing degree days, base 45°F
2,774
Growing degree days, base 50°F
1,736
Growing degree days, base 55°F
954
Growing degree days, base 60°F
417

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January79501
February67602
March651011
April494146
May3174169
June18715279
July7550440
August7051446
September19710264
October454072
November66607
December82501

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 6.6 km from Maple Valley. 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 USC00454486 (Landsburg). Public domain.