What data is used to determine the current weather conditions?

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Or where does this state come from? Like what determines "partly cloudy" vs "clear"? I have a PWS with a solar radiation sensor. Would a fluctuating value mean partly cloudy? Would the rainfall counter make it turn rainny? Or is this state just something that comes from the WU algo?

Any ideas would be appreciated.
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Posted 5 years ago

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Tim Roche, Official Rep

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Usually the value comes from a nearby airport that observes conditions
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I'm wondering the same thing.  My weather station is showing partly cloudy (which is correct) but on WU it's almost always showing raining (hasn't rained for days).  The closest airport is also showing partly cloudy.  I have run my PWS linked to WU for a few years now with no problems until just a few months ago.  Now it's almost always showing raining when it's bright and sunny.
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Conditions like that usually come from the airport, if the airport is close enough for the condition to be valid.  If the airport is too far from the PWS, there is no condition reported.