If We Don’t Have Air Conditioning, Should We Leave Our Windows Open Or Closed With The Fans Running?

We’ve got an old house with no air conditioning. It’s about 98 degrees outside and the house is getting HOT. We’ve got fans running in the rooms we are in and turn them off when we leave the room. Should we leave the windows open to help get air circulating (but let in the outside heat), or close them (keeping the already hot air in, but the super hot oustide air out)?
Best answer could help lots of people during all these heat waves.
Thanks.