 We were with Whitney as she treated a woman suffering from dehydration. How quickly can heat illnesses set in? It can happen within 15 minutes. South Texas is bracing for Barrow, which is likely to strike the area Monday. John Hall is with Texans on Mission. So we actually have volunteer teams that are on alert right now in Corpus. We have teams that are in the Rio Grande Valley, and so they will very much be the first ones to respond.