Thursday, May 28, 2009

Temperatures Across Washington State

Alright let's wrap up Washington climate today by talking about the temperatures.

It varies quite a bit depending on if you are west or east of the Cascade Mountains.

In meteorology, the difference between the daily high and low temperature is called the diurnal range.

Drier climates have a much larger diurnal range than more moist climates.

Here is an example from August 31, 2008.

On the western side of Washington, the city of Seattle had a high of 65 with a low of 51. That is a difference of 14 degrees.

On that same date, on the eastern side of Washington, where the climate is much drier, the city of Spokane had a high of 69 and a low of 42. That is a difference of 27 degrees.

Drier air warms up and cools down faster than air with more moisture in it.

Sometimes those drier climates can really heat up, but cool down just as quick. On August 17, 2008 -- Spokane saw a high of 103 degrees after a morning low of 68. That is a diurnal range of 35 degrees.

The state follows normal thinking in terms of the coldest months being December and January and the warmest time peaking around August.

In Seattle, temperatures range from the mid 40s in winter to the lower 70s during the summer -- on average.

There is a little more contrast in Spokane with winter temperatures averaging around 30 degrees for a high and summer averages in the lower to middle 80s.

So folks in eastern Washington see a little more contrast and change between the seasons as opposed to western Washington residents.

The entire state can see both cold and warm spells.

"Deep freeze" winters have been recorded statewide. One such winter was over 1955-56 where western Washington saw up to 6 feet of snow.

Snow stayed on the ground in some places for up to 3 months and both lakes and rivers completely froze.

It can also get very warm in Washington, especially across eastern Washington.

The National Weather Service office in Spokane did a great study called the Hottest Day Ever in the Pacific Northwest -- August 4, 1961.

Click here to read more.

The all-time record low for Seattle is 0 degrees and their all-time record high is 100 degrees.

However, that low is a little misleading because of Seattle's proximity to the waters of Puget Sound -- which protect the temperature. Just a matter of miles outside the city and away from the water it has been as low as 20 degrees below zero.

Compare that with Spokane whose all-time record low is -25 degrees and their all-time record high is 108 degrees.

For the state, the all-time record low has been recorded at 2 locations. It was -48 degrees at Mazama (elevation of 2,120 feet) and Winthrop (elevation of 1,755 feet). The date was December 30, 1968.

The all-time record high was 118 degrees last recorded on August 5, 1961 at Ice Harbor Dam, with an elevation was 475 feet.

So hopefully this has been interesting and you've learned a little something new about Washington state.

The summarize, the weather is highly variable from west to east. The western part of Washington is wet with not as much variability in annual temperatures compared to the much drier eastern part of the state.

I am sure there are a ton of micro-climates across Washington -- simply due to the varied topography and elevation changes between the two mountain ranges in the state.

For those interested in a much closer and detailed look at the climate of Washington, I've been told there is a great book called The Weather of the Pacific Northwest by Cliff Mass.

Cliff teaches atmospheric science at the U. of Washington -- Seattle.


  1. If you are interested in my book on Northwest Weather, there is more information at:

    or check amazon, barnes and noble, local book sores.

  2. Fantastic climate reports on Washington, Chris. It's hard to imagine that Seattle dropped to ZERO degrees. Amazing.

    Ever since my trip to Oregon last Summer I've been intrigued to learn more about the climate out there. I am assuming Oregon must be a bit similar to Washington?