How long ago did this begin?
To consider over-exposure, was he in the elements for any length of time or are the temps particularly high there?
Open beaked breathing?
After two days this is something you can't put off anymore - either get your vet out there or get him to the vet's.
It does appear that he's having some temperature control problems from what you're describing, but at this point the exposure issue (if that's what happened) should be resolved since he's now in a more controlled environment.
I think there's another problem, quite often it's a fungus/yeast, but there's no taking chances with a bird. Even a fungal or yeast infection needs to be attended to quickly or it can become very serious.
Since there is no way to know for sure that this is the problem, home treatments aren't suggested because they waste valuable time.
If your bird will drink and eat on their own, excellent. If not, have an eyedropper ready to administer a few drops of plain water, or better yet, children's Pedialyte ever 20-30 minutes. Put the dropper gently inside the beak and let the drops fall into the bottom beak under the tongue rather than trying to get into the back of the throat. We don't want to chance the bird inhaling the fluid and developing pneumonia.
Another feeding option is to offer ½ spoon of all natural, organic baby food (squash, yams, sweet potatoes, mixed vegetables) which many birds take readily; also try some pabulum or baby rice cereal and a few licks of natural (no artificial anything) yogurt.
These are just temporary supportive measures to keep your bird alive while you get professional, hands on care. These measures will not cure your bird.
Don't mistake what looks like recovery to be a real recovery. It is very common for a bird to regain enough strength to start hiding their illness again, but what's happening is that it's progressing and by the time you see symptoms again, it will be much worse or too late.
Please let me know how you both make out,
Certified Avian Specialist
Cert. Avian Specialist; Int. Assoc.Animal Behavior Consult; Pet Ind. Joint Advisory Council; author