Measuring the Weather
What's measured by the weather station
on the roof above you?
The meters on the left report the current weather from instruments
on Pacific Science Center's roof.
This information is stored on our weather station computer, which
sends it to computers at KING 5 and the National Weather Service.
Wind speed and direction
Winds are referred to by the direction from which they blow. A
north wind is one which blows from the north.
In Seattle, a north wind usually means a high pressure system
and dry weather are approaching. A wind shift to the south usually
means the approach of a low pressure system and wetter weather.
Relative humidity
Relative humidity is a percentage of moisture in the air as compared
to the maximum amount of moisture the air can hold. This maximum
varies with temperature-warm air can hold more moisture than
cool air.
Temperature
Temperatures in Western Washington tend not to be as hot or as
cold as temperatures in Eastern Washington. This is because water
heats and cools more slowly than land. Because Western Washington
is surrounded by the Pacific Ocean and Puget Sound, air temperature
changes more slowly than in Eastern Washington, where water is
scarce.
Wind chill/heat index
The combination of temperature, humidity and wind speed can make
the air feel hotter or cooler than the actual temperature. Wind
makes us feel cooler. High humidity makes a hot day feel hotter.
Dew point
Dew point is the temperature at which air becomes saturated, or
unable to hold additional moisture. Warm air can hold more water
vapor than cool air. When the temperature drops during the night,
the air can't hold as much moisture, and dew forms.
Barometer
Barometric pressure is a measure of the weight of the air pressing
down on us. Cold, dry air weighs more than warm, moist air. Watching
how the pressure changes over time tells more than the pressure
alone. Rising pressure usually indicates that a high pressure
system is approaching, typically bringing clearing skies. Falling
pressure usually means a low pressure system is approaching, often
bringing clouds and precipitation. Rapid changes in pressure warn
of strong winds.
Light
The sun's rays provide the energy that drives the weather. This
meter shows the current percentage of sunlight relative to the
amount of sun at noon on a clear summer day.
Rainfall
The average rainfall in Seattle is about 38 inches per year.
Average rainfall in inches
- January 6.0"
- February 4.2"
- March 3.6"
- April 2.4"
- May 1.6"
- June 1.4"
- July 0.7"
- August 1.3"
- September 2.0"
- October 3.4"
- November 5.6"
- December 6.3"
|
