I don’t know about the men, but the ladies can wear a cool dress during the hot summer. That shouldn’t be an excuse.
It doesn't have to be suit and tie. Clean long pants (starting at $10 at Walmart), a clean tucked in polo or short-sleeved buttoned shirt (starting at $5 at Walmart), and hard leather shoes (starting at $25 at Walmart) is perfectly fine, respectable summer attire.
I'll forgo pricing underwear and belts, but for the price of a dinner and movies for two, a man can look decent and be comfortable.