The physical footprint of a data center is far smaller than a city, so that would limit heat island effects that arise from things like surface albedo (which are only material over large areas). In terms of raw heat dissipation though, an exceptionally large data center could compete with a small city.

Not when a datacenter is the size of manhattan

Yeah, but I’m wondering if they are hotter or more consistently hotter than a city which while hotter than a forest still has trees and parks etc.