Jeff Renner's Top 10
1. Why is there such a big difference in the weather between Western Washington and Eastern Washington?
The Cascades usually prevent the moist ocean air, which dominates
weather in Western Washington, from reaching Eastern Washington.
Moist air changes temperature more slowly than dry air, which
keeps average summer temperatures in Western Washington in the
low-mid 70s. It also keeps winter temperatures from plunging into
a deep freeze very often. Eastern Washington summer temperatures
average in the mid-upper 80s. The drier air east of the Cascades
can heat up or cool down rapidly, resulting in greater extremes in
temperature throughout the year.
2. Is Puget Sound really the wettest area in the country?
Not at all. Seattle, for example, is well down the list of major
cities when it come to yearly rainfall, trailing even Boston,
Miami and Atlanta. Seattle averages 38 inches of rain each year,
while Boston averages 44 inches, Atlanta 48 inches and Miami 57
3. What are the wettest and driest days of the year?
The driest day in the Seattle area has historically been August
4, when it has rained only six times in the past century. The
wettest day? November 19, when it's rained 74 times over the past
4. Why are some areas, such as Bellingham and Enumclaw, so much windier than others?
Wind is the result of air moving from high pressure areas into
low. The bigger the difference in pressure between two places,
the faster the wind moves. When this air is forced through a narrow
gap such as a mountain pass, it speeds up evens more. That's why
areas such as Bellingham and Enumclaw, which are near mountain
passes or river valleys, often record the highest wind speeds
in Western Washington.
5. What exactly is high pressure? What about low pressure?
High pressure is an area of sinking air. As it sinks, the air
warms and tends to evaporate moisture, and that's why we often
associate clearing skies with high pressure. Low pressure is an
area of rising air that cools, causing the water vapor to condense
into cloud droplets, raindrops or snowflakes.
6. What's the difference between "rain" and "rain showers" in the forecast?
Meteorologists forecast "rain" when they expect the
wide, flat stratus clouds that produce rainfall over large areas.
When puffy cumulus clouds are expected, meteorologists forecast
"rain showers" because these clouds may cause rainfall
over your house, while your neighbor across the street might remain
7. Why does the weather vary so much from one spot in Western Washington to another?
Fly across Washington State and you'll find few flat areas. This
state, particularly the western half, is covered with mountains
and hills. Air rising up a hill or mountain cools, which in turn
tends to create or enlarge clouds and increase their ability to
produce rain or snow. Conversely, air sinking down the back side
of a hill or mountain gets warmer, which tends to destroy or reduce
clouds and their ability to produce rain or snow. For that reason,
changes in the wind direction and the presence of hills and mountains
make a big difference in local weather.
8. Is weather tougher to forecast in Western Washington than other places?
Yes. Western Washington is considered one of the most difficult
places to forecast weather for several reasons. Most storms approach
us from over the Pacific Ocean, where there are few weather observation
stations. Our region's many mountains and hills also produce weather
that differs a lot over short distances.
9. When does Western Washington usually get its first snowfall?
December 3 marks Western Washington's average first day of snowfall.
We have a 13% chance of having a "White Christmas."
10. When does the first killing frost usually arrive in Western Washington?
The earliest killing frost officially recorded in the Seattle area was on October 16, 1946. The average data for the first killing frost is November 2. However, rural areas, especially sheltered valleys, will often experience an earlier killing frost.