Depends on where very dramatically. If the A/C units are venting to the outside, not likely to have a dramatic impact outside the immediate area of the coils.

Depends on where very dramatically. If the A/C units are venting to the outside, not likely to have a dramatic impact outside the immediate area of the coils. In the NYC subway system however, it apparently had a dramatic impact. From what I read (source not handy), before A/C came to trains the tunnels were relatively ok (<90°F), but since adding A/C to the trains, tunnels and platforms now hit way over 100° (L platform has been >115°) in the summer.