that was before heat generating electrical devices were added to the mix such as AC units and sky scrapers with reflective glass that concentrates the warmth as it reflects. Low E windows are good at reducing the energy that enters a house but are devastating to plants where that energy is reflected to.
Several weeks ago I was watching the weather and it was showing radar of the snow in the St. Louis area. I noticed something that I think was an example of UHI. The system had a counter clockwise rotation with snow to the west of St. Louis. Over St. Louis no snow was shown on radar. But snow was reappearing on the east side of St. Louis. Seemed to me that the extra warmth of the buildings was enough to warm the air and cause the snow to melt as it was falling through the air. The same clouds were again producing snow after they had moved away from warmer St. Louis.
Real Science 
that was before heat generating electrical devices were added to the mix such as AC units and sky scrapers with reflective glass that concentrates the warmth as it reflects. Low E windows are good at reducing the energy that enters a house but are devastating to plants where that energy is reflected to.
Several weeks ago I was watching the weather and it was showing radar of the snow in the St. Louis area. I noticed something that I think was an example of UHI. The system had a counter clockwise rotation with snow to the west of St. Louis. Over St. Louis no snow was shown on radar. But snow was reappearing on the east side of St. Louis. Seemed to me that the extra warmth of the buildings was enough to warm the air and cause the snow to melt as it was falling through the air. The same clouds were again producing snow after they had moved away from warmer St. Louis.