This getup with a white crew-neck t-shirt and a grey crew-neck t-shirt isn't a hard one to pull off and leaves room to more sartorial experimentation. Break up this look by sporting a pair of white slip-on sneakers. There are a variety of ways to look neat and survive the heatwave, and that's one of them. This getup should clear any doubts you had about wearing casual clothes as a 40-year-old gentleman.