Urban Heat Island Effect

I did more Step Test-prep with Ms. S again today, and I have another interesting cultural effect to share from it. Here is the passage she was given (to answer questions from:

Urban Heat Island Effect
Urban areas are covered with concrete, which absorbs heat from the sun, and have fewer plants and trees. This causes the heat island efect, as one area gets hotter than those which surround it. Now, both governments and people are dealing with this problem. Local governemnts encourage planting on the roofs or even on the walls. Peope sprinkle water around their houses in the evening.

I wanted to share this passage, because I hadn't heard about Urban Heat Effect before coming to Japan (maybe because it is the Urban Heat Island Effect - and I'm from the midwest?). I mean, Minneapolis is pretty big and it gets really hot and humid in the summer, but maybe I had never heard about this theory before because most people in MN combat the warm summer sun with air conditioning (vs. more fans here - or because the sun is not too violent for us to be outside and enjoy it so we don't mind).
Anyways, the part about sprinkling water to cool off the air is pretty common practice here and I think it's a realistic solution. At my friend Lena's apartment, the landlord sends a notice to all residents on the night before a really hot day that they should water their plants, under the belief that this practice will help alleviate the heat (even as much as a few degrees celsius). According to Lena, it actually works.
It seems like having potted plants outside seems more popular here than at home, but now I am considering buying a few for my little place or balcony and testing the theory. I'll take pictures if I do.