Small bumps on forehead when it’s hot?

Hello lovely humans <3 I was wondering if anybody has a similar experience or could give me some advice about what to do. Whenever it gets very hot/ humid (common in summer where I’m from), I get these tiny raised bumps on my forehead ? They are barely noticeable usually but as soon as it’s hot they become very noticeable. I’m currently using retin-A once a week to get rid of the bumps totally but I’m not sure if this is even the right approach.. Any help or advice would be so appreciated ! TIA :-)