Sea-Tac's temp sensor actually reading slightly cooler than it should

    A 90 degree day in Seattle this week. (Or so says Sea-Tac Airport's thermometer.)

    SEATTLE -- Well, it turns out the thermometer at Sea-Tac Airport is off slightly -- reporting temperatures slightly cooler than it should. Sea-Tac is the official reporting station for Seattle.

    The National Weather Service sent out a technician to check out the weather station at the airport after UW Professor and weather blogger Cliff Mass posted a blog speculating the station was reading temperatures hotter than it should. Tests showed the thermometer was actually recording temperatures between .6 and .82 degrees cooler than it should.

    NWS Meteorologist Mike McFarland said that's within the tolerances the Weather Services requires of its weather stations so Thursday's high of 92 is official and correct along with the rest of this week's 90-degree readings.

    In a Wednesday blog post, Mass pointed out that a thermometer just 10 blocks away was consistently running 3-4 degrees cooler than Sea-Tac, and that on Wednesday, Sea-Tac showed a high of 92 while all other sensors in the area ranged from 88-90. Even Boeing Field, which Mass says should be hotter based on geography, has been cooler this week (89, 88, and 89) than Sea-Tac (90, 91, 92).

    There have been issues with Sea-Tac's gauge before. In 2014, a similar warming problem popped up and corrected itself when the gauge was replaced. And earlier this year, Yakima was running several degrees hot until the sensor was replaced and again, the problem corrected itself.

    But it turns out this time, the sensor at Sea-Tac was reading the correct temperature.

    Why don't they just move the gauge to Seattle proper?

    It does seem strange to many that for as large of a city Seattle is, we essentially get our official weather report from Burien.

    Before airplane travel and airports were widespread, observations were taken in city locations -- for Seattle, it used to be taken at the Downtown Federal Building. The official reporting station moved to Sea-Tac when it opened in 1945 because it was decided it was best to have your most accurate data and observations for pilots at the runways, so that's why most official stations now at airports. The primary function of the instruments is to provide crucial weather information to pilots with climate tracking/weather geekery a secondary mission, so that's where the weather observers were stationed.

    But now all weather observations are automated so you could conceivably move Seattle's official spot somewhere closer to the city and maintain similar standards. The NWS office at Sand Point has been taking official weather measurements for climate tracking since 1986. Perhaps someday once they get a few more decades under their belt we can move our official spot there, but last I heard there are no plans to do so in the near future.

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