Being hot and uncomfortable doesn’t make you grouchy? Violent crime does tend to rise in the summer months. Maybe opportunity, but maybe mood.
If figure this is a public service announcement. “The heat is making you grouchy. Try to rise above it. Try to stay cool.” In other words, it’s asking people to be self-aware and take responsibility, not providing excuses as some here think.
When it gets too hot they start staying inside and crime goes down.