Not even W/V measuring units along a RWY can be trusted. I remember a long discussion with a MET chap (whose position was on a mayor airport) who noted bizarre wind values, even on quiet days. He found out the units could pick up vortices from departing A/C's wake.
Normally the MET observers would discard the readings as "spurious" signals, but later those values were auto-inserted in reports like ATIS.
When reporting that to his superiors he was told to shut up because in that time the MET service wanted to go fully automatic w/o any human intervention anymore.... and said that if the readings were like they were, the pilots needed to be warned for that......