Like many other types, there’s a wide range of garage fans. All the way from sawdust clearers to near-jet engine levels of gust.
The CFM you need depends on how you intend to use the fan. If you’re looking to keep an entire large garage ventilated, you’ll want to consider fans pushing 5000 CFM and above. However, if you’re looking for a bit of cool air on your face in a small area, even the lowest power fan will suffice.