30-year climate normals

Cowlitz County Climate and Weather Averages

Hottest month — August

82.3°

average daily high. The coldest month is December, averaging a low of 37.2°F.

Cowlitz County gets 40.66" of precipitation a year, and 42% of it falls in Nov, Dec, Jan.

Temperature through the year

Each bar spans the average daily low to the average daily high for that month.

Month	Avg high	Avg low	Precip
January	46.7°	37.3°	5.01"
February	51.0°	37.7°	3.71"
March	56.7°	40.0°	4.41"
April	61.7°	43.2°	3.58"
May	68.9°	48.9°	2.91"
June	74.0°	53.0°	2.11"
July	81.6°	56.8°	0.55"
August	82.3°	56.9°	0.63"
September	76.4°	52.4°	1.75"
October	64.1°	46.4°	4.02"
November	52.6°	41.6°	5.83"
December	46.0°	37.2°	6.15"

Rainfall by month

Precipitation is spread fairly evenly through the year here, with 42% falling in the wettest three months (Nov, Dec, Jan).

January 5.01"

February 3.71"

March 4.41"

April 3.58"

May 2.91"

June 2.11"

July 0.55"

August 0.63"

September 1.75"

October 4.02"

November 5.83"

December 6.15"

Annual total 40.66"

What this climate costs you

Degree days measure how hard a building has to work to stay comfortable. They are the reason two identical houses have very different power bills, and they are the link between the weather here and what you pay every month.

Cooling degree days How much air conditioning the climate demands 427

Heating degree days How much heating the climate demands 4,155

Approximate annual cooling cost At 14.95¢/kWh, Washington average $64

Approximate annual electric heating cost Lower where heating is gas rather than electric $217

These are rough planning figures from degree days and the state electricity price, not a bill estimate. House size, insulation and fuel type move them a lot. See the full cost of owning a home in Cowlitz County, where electricity is one line of eight.

Common questions

What is the weather like in Cowlitz County?

Cowlitz County averages a high of 82.3°F in August and a low of 37.2°F in December. Annual precipitation is 40.66 inches, with essentially no snow.

When is the rainy season in Cowlitz County?

The wettest stretch is Nov, Dec, Jan, which accounts for 42% of the year's precipitation. Precipitation is relatively evenly distributed across the year.

How hot does it get in Cowlitz County?

The average daily high in August, the hottest month, is 82.3°F. That drives 427 cooling degree days a year, which is what your air conditioning has to work against.

Does it snow in Cowlitz County?

Effectively no. Measurable snowfall is rare in Cowlitz County.

Sources

Temperature, precipitation and snowfall normals — NOAA National Centers for Environmental Information, 1991–2020 Monthly Climate Normals, station PORTLAND TROUTDALE AP, OR US (USW00024242), 46.5 miles from the county centroid.
Heating and cooling degree days — NOAA, same station and period.
Electricity price — US Energy Information Administration, Electric Power Monthly Table 5.6.A, Washington residential average.
Wet-season share is the wettest three consecutive months as a percentage of annual precipitation, calculated from the monthly normals.