I don't know about most cities but here in STL, we have an entire grid of temps across the entire metro area.  So I see the variations all over the city.  Having said that, here in STL I know our "official" weather is taken at the airport, which is not even in the "city" of St. Louis. That airport I'm sure has a type of heat island effect, expecially with the new runway just openend and the density of the surrounding area (BOEING is on the other side).

I don't think the airport was there during the dust bowl days, but you'll have to take my word for it b/c I wasnt around.  We also have a lot of weather instruments (radar etc) set up in the rural areas so I'm sure the readings are different there too.  I think it's hard to be accurate on temps when so many other variables seem to shift the focus a bit each time until you're off course entirely.

All of you missed the point.  I wasn't saying the HIE affects GW, but rather the readings on the ground.  Prior to the inception of the airport I don't know where they got the official temps. Let's even go far and say they took readings in the same spot and decades later an airport gets built and when you look at the temps, they appear to be masked as higher b/c of HIE.  My only point is that temps need to be consistent in their location to really be accurate.