My cat does this when he eats anything moldy (food left in the bowl too long) or the top or bottom portion of any bag of dry food. Did you start a new bag of food, or are you at the end of a bag of food? Or have you used the same food bowl for a while in this heat?

That's what I would do. If there's an emergency vet near you, it might be worth making a phone call to ask about it, but good chance they'll refer you to your regular vet anyway.

My 12 year old cat has always been a vomiter, usually due to eating too quickly. Earlier this evening, he vomited bile, no food. About an hour later, he vomited more bike, this time red tinged. Other than being a little slow this evening, he was acting normal for most of the day, including identifying that we have a mouse in the kitchen this morning. I'll call the vet in the morning, unless the vomiting becomes more frequent, right?