Napavine climate

Napavine Frost Dates and Growing Season

NOAA 1991-2020 normals for Centralia, 16.5 km from Napavine, elevation 185 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Centralia. 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 22 and the first fall freeze around October 27, a growing season of about 188 days.

Median at 36°F
last May 7, first October 8
Median at 32°F
last April 22, first October 27
Median at 28°F
last March 23, first November 13

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 24May 18May 14May 11May 7May 4May 1Apr 28Apr 24
32°FMay 10May 4Apr 30Apr 26Apr 22Apr 18Apr 12Apr 5Mar 30
28°FApr 17Apr 6Mar 31Mar 27Mar 23Mar 18Mar 12Mar 4Feb 24
24°FMar 17Mar 8Mar 2Feb 26Feb 20Feb 14Feb 3Jan 21Jan 2
20°FMar 4Feb 25Feb 17Feb 8Jan 27Jan 13Jan 2Dec 22Dec 10
16°FFeb 25Feb 15Feb 1Jan 12Jan 1Dec 24Dec 16Dec 9Dec 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 22Sep 29Oct 1Oct 5Oct 8Oct 13Oct 17Oct 21Oct 26
32°FOct 7Oct 15Oct 19Oct 23Oct 27Oct 31Nov 3Nov 8Nov 17
28°FOct 21Oct 30Nov 4Nov 8Nov 13Nov 17Nov 22Nov 28Dec 7
24°FNov 6Nov 13Nov 19Nov 25Nov 30Dec 6Dec 12Dec 21Jan 1
20°FNov 17Nov 27Dec 3Dec 9Dec 16Dec 23Jan 1Jan 12Feb 8
16°FNov 27Dec 3Dec 7Dec 13Dec 22Dec 31Jan 10Feb 2Feb 19

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°F178170163158154150144138130
32°F215206199193188184178172163
28°F269257249242234228221212200
24°F333317304295286277269260248
20°F365360348338329319309300284
16°F365365365365365357343332316

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
83% of years
16°F or colder
47% 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
5,063
Cooling degree days, base 65°F
164
Growing degree days, base 40°F
4,469
Growing degree days, base 45°F
3,051
Growing degree days, base 50°F
1,943
Growing degree days, base 55°F
1,104
Growing degree days, base 60°F
504

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January77002
February65204
March620014
April471053
May2984183
June16518303
July5763471
August4964480
September15015316
October4060101
November633013
December79202

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 16.5 km from Napavine. 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 USC00451276 (Centralia). Public domain.