Second all of the above with a couple caveats. Everyone needs a different amount of water when running over the summer. It all depends on your conditioning and how much you sweat. Personally speaking, I'd be way too bloated if I were consuming 10 ounces per mile.
And when it comes to gels, they are much better at replacing calories but less effective at replacing electrolytes, hence the need for salt tabs in the summer or basically whenever you sweat a bunch. The other word of caution with gels is that you have to test a bunch to make sure they're compatible with your gut. GUs are notoriously hard on the gut. I've experimented with a bunch (GU, Huma, Honey Stinger, Clif Bloks, Hammer) but ultimately settled on Maurten which are just fantastic. They taste great and go down easy. You can also go the drink mix route which is great pre-run or during. I highly recommend Maurten once again, Tailwind, nuun, or Skratch.