WeatherWhys for June 25,2014 from accuweather.com

Heat tops the list the 10-year average of weather-related deaths across the United States, exceeding tornadoes and hurricanes. One place that heat can kill is in a vehicle. Short wave emerging from the sun enters the vehicle through the glass windows with ease. Once inside, this energy heats up interior surfaces, which in turn gives off long-wave radiation. This long-wave radiation cannot escape through the glass and causes the vehicle to heat up even further. In less than 30 minutes, the heat can become deadly.