I'm not sure if the same is true for Corgis, but we had a black chow mix rescue dog staying at our kennel not too long ago. When the summer started up we felt so bad for him being out in the horrible heat and humidity - he loved being out with the other dogs in daycare but would just get so
hot! We asked one of our groomers if it would be better for him to be shaved. She said its actually better for them to have their coats, that their hair somehow keeps them cooler. I dont remember exactly how she explained it. I'm not even sure if thats right, but she usually knows what she's talking about.
I think as long as you dont keep him outside for long periods and make sure he always has water when he is out in the heat, he should be fine.
