How to fix an urban heat island effect: plant street trees, it is that simple, that can improve the urban heat island effect, if you want downtowns to be livable, just plant trees, they naturally cool areas and provide shade, plus they're pretty. There is no reason not to plant street trees other than the budget and if thats an issue just cut the police budgets by a few million
Yes, I know that the issue is more complicated than that, but it is such a simple solution and cities just fucking, don't do it
"We can't do that because it would mean removing parking spots to make room for trees."
"We can't do that because all the air pollution from cars kills most trees."
If you reduce the dependency on cars these two objections no longer apply. win-win.
Also cars are one of the largest creator of urban heat so reducing car dependence reduces the heat island effect