It might be useful to have his urine tested.
You can take a urine sample yourself, by feeding him a bit of cucumber or other watery food and sitting him on some plastic. Wait for some time, so your boy has time for several pees. Suck them up with a syringe and store the filled syringe in the fridge (best in a little freezer or plastic bag) until you go to the vets.
Unfortunately, increeased thirst is such a vague sign that it will be difficult to determine whether there is something wrong.
For diabetes, you would like to look out for weight loss; for UTI for blood in the urine (which NOT necessarily means red urine!) and peeing pain.
It can well be that he is OK. I hope that Rodney is!
The other question - in warm weather, they can drink more. Are you in the South? In this case, it can well be just the warm weather!