Climate models are made out of all of these cells. The are typically about 10 km on edge (62 miles). Temperature analysis is done on a gridded basis. The scientists do not use the obviously heat modified temperatures of urban weather stations unadjusted. That would be unintelligent. The weather stations in each grid are all averaged together to get a number for that grid, if there are none, or there is a metropolitan area in a grid – the individual stations are evaluated and the heat island effect is "adjusted" out of the warmer station.