I've lived in Houston since '95 and a fair amount of what people think about the weather is not correct. Yes, it's humid and salty near the Gulf but it doesn't take many miles to get away from the salty part. As for humidity, it's no worse than Austin and it rains less here than Austin, too.

I don't leave my guns outdoors but I can leave bare steel in my shop for a very reasonable amount of time before it starts to rust.