Kennewick climate

Kennewick Frost Dates and Growing Season

NOAA 1991-2020 normals for Kennewick, 2.8 km from Kennewick, elevation 390 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Kennewick. 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 March 28 and the first fall freeze around October 30, a growing season of about 216 days.

Median at 36°F
last April 14, first October 21
Median at 32°F
last March 28, first October 30
Median at 28°F
last March 8, first November 11

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

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°FOct 7Oct 12Oct 15Oct 18Oct 21Oct 23Oct 26Oct 29Nov 2
32°FOct 18Oct 22Oct 25Oct 28Oct 30Nov 2Nov 5Nov 10Nov 15
28°FOct 27Oct 31Nov 4Nov 7Nov 11Nov 15Nov 20Nov 24Dec 1
24°FNov 5Nov 11Nov 16Nov 21Nov 25Nov 30Dec 4Dec 10Dec 20
20°FNov 15Nov 24Dec 1Dec 5Dec 10Dec 16Dec 24Jan 1Jan 12
16°FNov 26Dec 4Dec 10Dec 17Dec 23Dec 30Jan 5Jan 14Feb 1

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°F208203198194189185180175168
32°F239231226221216213209203196
28°F273263258252246241236231223
24°F312301292285277270264257247
20°F349334327319309301293283272
16°F365364356347336329320311297

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
97% of years
16°F or colder
84% 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
4,619
Cooling degree days, base 65°F
1,020
Growing degree days, base 40°F
6,075
Growing degree days, base 45°F
4,693
Growing degree days, base 50°F
3,502
Growing degree days, base 55°F
2,503
Growing degree days, base 60°F
1,680

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January91603
February71405
March558037
April3233150
May12553394
June25151576
July1367830
August2337799
September49105506
October3305174
November663024
December91304

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 2.8 km from Kennewick. 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 USC00454154 (Kennewick). Public domain.