Prometheus says...

It dropped the temperature in my old shop from scorching hot to
whatever temperature it was outside in a matter of minutes, and it
sounds like you have exactly the same situation in yours. IIRC, they
had some vent fans that mounted directly to the inside of the roof
right next to the ones mounted on the wall at the hardware store, so
that may be easier.

If they are in the roof, what about rain? Or maybe you are talking
about a hooded vent?