We had 90+ degree days for 3 days in a row (and upper 80's before/after that) Night time temperatures dropped into the 60's, so by turning on the fan at night

We had 90+ degree days for 3 days in a row (and upper 80's before/after that) Night time temperatures dropped into the 60's, so by turning on the fan at night (which blew air out and upstairs window, bringing in the cool air in throughout the house), I think we would have been fine even in a longer heat wave. By morning, it was cool enough to need a blanket in bed. If temps didn't drop so significantly at night, then we may have had more problems. The house is standard wood-frame construction, so doesn't have a lot of thermal mass, though it is on a concrete slab, so that may have kept the downstairs cooler.