[fwdude]

What on earth did people do in the past when cars didn’t have a/c ?

Left their windows rolled down. This was ALWAYS the case with us as small children.

[JCBreckenridge]

Same. I rode cross country as a kid. In a camper. Windows rolled down. Never had any issues.

[lonestar]

Also, people left early to try to get to their destinations before the hottest part of the day.

Driving from TX to CA, people timed to cross the desert at night.