Ideas? what medical problems can hypothermia cause?

Depends on severity: Mild hypothermia, usually no lasting damage. More severe, there is lack of oxygen to tissues leading to frostbite, gangrene, fluid in the lungs, pneumonia, kidney failure, heart problems. You can get changes in heart rate, slowed breathing, changes in consciousness, with slurred speech, staggering walk and unresponsiveness. Kind of an odd topic for summer.