Temperatures 5 to 10 degrees above normal will prevail today, rising above the century mark for the western two-thirds of the county warning area. Acting with robust relative humidity values, these temperatures will produce elevated heat index readings this afternoon for all of deep South Texas and the Rio Grande Valley except for the Barrier Islands. Upper heat index readings will range between 105 and 110 degrees this afternoon. Some areas may briefly experience heat index readings of 111 to 112 degrees. If working outside today, be sure to drink plenty of water, wear loose-fitting and light-colored clothing, and take frequent breaks in air-conditioned locations. Be sure to check on elderly and infirm neighbors and relatives, provide shade and fresh water for outdoor pets and livestock, and check the backseat of your vehicle when transporting children.