If we relax "never" to "not more than 60 days a year", that would be most of Canada, northern US, most of Europe and Russia. No idea what's going on in southern hemisphere, but I guess Argentina/Chile and southern Australia are the same.

This obsession with mold looks to me as an exclusively US thing. I have no first-hand data but I guess it's due to insufficient air flow combined with air conditioners pushing humidity all the way up.

Mold is an issue in Finland, mostly for insulated houses with poor ventilation. Many schools and public buildings have mold and other air issues due to saving on heating.

It's pretty rare for it to get above 25C where we live in Scotland - pretty sure it didn't get that warm at all this year.