Anything is OK - providing your cover options can deal with it. Can't comment as a Southerner of course!
I know it's not quite as hot up here in PA in summer but - not far short at times!
I manage with t-shirt and shorts - with the extra of a Smith and Alexander vest when I have to go out. That is often biking so, a vest does not seem too odd. A long but thin open shirt also gives good cover - patterned is best.
A G19 should be manageable for many - as long as cover options suit - as ever, best to dress to carry.