On bright summer days we may remember to apply the sunscreen, but we may not remember to give the heat the full respect it deserves. When temperatures soar, Mayo Clinic experts say we need to take precautions. We also need to be on guard for the warning signs of overheating. Family medicine physician Jennifer Nordstrom, M.D., at Mayo Clinic Health System in La Crosse, Wisc., says heat illness can range in severity from mild heat cramps to heat exhaustion to a potentially life-threatening heatstroke. She says certain individuals are at higher risk in the heat.