ST tires are not designed to handle heat buildup, LT tires are. If you have 15 inch rims you can get 113 load range (2550lbs) tires but you may want to go up to 16 inch to get a higher load range rated LT tire.
Heat not load causes most blowouts. If you are not running with low air pressure or driving over the recommended speed for ST tires (the main culprits for ST tire blowouts) then it is may be the heat of the day. Blowouts are a summer event in ST tires. If you are driving 80, on a hot day, with low tire pressure you are headed for a blowout ;)