The weather info from those instruments is meant for airport ops, not climate. And besides, almost the entire record is UHI contaminated, anyway. I've seen small town readings higher like airports because of infrastructure, compared to the truly rural sites. NOAA has invested in the US Climate Reference Network to get a better handle on this issue. Don't know how that is going at the moment, but even they know through studies in recent years how much infrastructure contaminates temperatures. Anthony Watts really brought that to light with his study a decade ago, and NOAA acknowledged his work, and confirmed it. NOAA even did a study on site placement near and away from structures, and found significance there. But no matter what, a cooling/warming signal will always emerge from that noise. Just takes a while.