Go for a straightforward but casually cool option by marrying a navy linen long sleeve shirt and sweatpants. You can get a little creative on the shoe front and complement your ensemble with a pair of white slip-on sneakers. As you know, the key to getting through the hottest time of year is opting for cool ensembles like this one. Those who are curious whether you can still pull off cool casual looks as you slip into your 40s, this outfit should answer your question.