Monday, May 18, 2009

Precipitation In Washington State

For those of us outside of the Pacific Northwest and Washington state, if someone says describe the weather in Washington -- I think many would say wet.

This, of course, is because of all the press the Seattle area and the mountains get during the weather segment, especially during the cool season.

But actually, using the term wet completely depends on which side of the Cascade Mountains you reside. This is clear on the map below.

West of the Cascades you will find a wetter climate than you will for locations east of the mountain chain.

Let's break it down by a few cities and on the state level.

Overall, the statewide average precipitation is a whopping 38.44 inches, but this is heavily skewed by the western portion of Washington.

Here is the average annual precipitation for some selected cities...and the average annual snowfall.

  • Quillayute -- 101.72" (10.9 inches of snow)
  • Hoquiam -- 68.69" (2.7" of snow)
  • Vancouver -- 41.92" (6.5" of snow)
  • Seattle -- 37.07" (7.1" of snow)
  • Bellingham -- 36.25" (11.2" of snow)
  • Spokane -- 16.67" (45.6" of snow)
  • Yakima -- 8.26" (23.5" of snow)

    Not too many states can boast that type of varied annual precipitation on a 300 mile road trip between Quillayute and Yakima.

    By the way, Yakima is sometimes referred to as "the Palm Springs of Washington" due to it having such an arid climate.

    The dry climate makes it a great apple growing area, one of the best in the world in fact. And approximately 75% of all hops grown in the United States come from this region.

    Every state in the nation has local weather phenomena called micro-climates. These are small-scale, unique weather patterns due to the local geography.

    I think some of these micro-climate are most obvious when we get into the western states that have such dramatic differences in elevation over a small area.

    Washington has a local weather feature called the Puget Sound Convergence Zone. This impacts a lot of people since much of the state's population lives along the Puget Sound, including the Seattle metropolitan area.

    As air flows around the Olympic Mountains on the west coast of Washington, it converges to the east over the Puget Sound vicinity.

    This enhances the precipitation in that part of the state.

    Click here to watch a great slideshow that will better explain the Puget Sound Convergence Zone.

    While most of the Olympic Peninsula receives copious amounts of annual precipitation, there is one area that is drier and warmer than the rest of the region on average.

    That is the northeast part of the Olympic Peninsula and the adjacent San Juan Islands, around the town of Sequim.

    This region sits in an area called the Banana Belt.

    The Banana Belt is a loose term used in the weather and climate world to describe an area within a larger area that sees drier and warmer temperatures than the surrounding region, especially during the cold season.

    Other states have "Banana Belts" including Colorado, Michigan and South Dakota.

    Tomorrow we will continue talking about the climate of Washington.
  • 1 comment:

    1. The area around Sequim (pronounced squim)and the San Juans have what we call out here a "rain shadow". It is very interesting to note that while in Seattle and Olympia it is raining, it may be sunny and clear up in Sequim and the San Juans.

      I now live in Eastern Washington. I came from Tenino near Olympia where most of the rain resides. I am now in a very arid region, and am dealing with rattlesnakes and scorpions. In Olympia the only snakes we had were garter snakes. What a significant difference in climate, flora and fauna.