I combined a couple threads here because they were both talking abou the same issue. And that issue is actually two issues, both of which are resolved at this point:
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Wind direction is undefined (null) when wind speed is zero. Yes, this is true. We do report the direction as zero (not NULL) in the wind data, but it should be NULL, since wind direction is undefined when wind speed is zero. We may address this in a future firmware update, although it would probably break a lot of things downstream - the toothpaste is out of the tube, so to speak.
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Zero values for direction should not be reported or counted as “North” when speed is zero. Also true! In the Smart Weather apps, wind direction is displayed as “—” when wind speed is zero. And these values are not used in the calculation of the direction average. Third-party applications should also implement that business rule: when wind speed is zero, direction is undefined.
For more discussion on how to calculate “average direction”, check out this thread: Calculate wind vector-direction