I set cooler in evenings and turn it up higher overnight.  I do this from mid to late June to mid to late September?  mid May to mid June and early and mid October depending on the year, I turn on For a couple of hours late evening cold temperature and then shut off overnight.  It's enough.  I could prob open windows but I am on a lower floor and some rare nights douches talk loudly, make noises, loud Coupang delivery trucks overnight, loud delivery scooters until late, etc.  Got to close window and use ac instead (for part of the time). 

Mostly lower to mid 20s is enough.  But there is a week in August really hot and humid and I need it set lower plus using a fan at the same time briefly.