I try to dress as functionally as possible, yet keep myself clean cut looking. However, it probably does vary a lot by region. It's 79 outside right now on Feb. 4 (sorry, had to). But that might give you an idea of some of the heat we deal with later in the year. I wear brown ankle high boots, and either cargo pants or khakis if possible. As for shirts, I keep it logo free, however I don't always wear a collared shirt. In the hottest months, I do wear cargo shorts. Cargos are great because you can keep a small tape measure, as well as your camera, wallet, and any other little items you might feel will help with your inspection, right there in one of the pockets. I don't like wearing shorts because of the vegetation that springs up overnight down here. (along with everything living on that vegetation) From saw grass cuts, fleas, to spider bites, my legs get torn up. I could never show up at a house in flip flops. I've found myself ankle deep in mud before, as well as other similar looking but worse smelling substances. They're rugged, and they're low profile, especially with pants. I do keep a baseball cap handy in the car for some of the more ragged looking homes. I've been in some hoarders homes where I've just been pounced on by fleas as soon as I walked in the door.
So keep it functional, but neat.