I'm worried about my cat....

He's acting a bit lethargic and feels somewhat warmer than usual. I know the a/c was out for several days and was just fixed yesterday morning. He also vomited during that time which he hadn't done for a while. I'm wondering if he's just trying to recover from the heat - or if he was reacting to the thunderstorm that happened tonight - or if he's ill. Sitting with us more quietly than usual...sitting in weird positions...finding weird places to lay. I'm worried.

If he doesn't show improvement by tomorrow, I'm taking him to the vet first thing on Monday. I have pet insurance on him, so hopefully it won't be too expensive. I just want him to be ok.