This smells like the Superbowl Sunday wife-beating hoax to me.
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.