Heat indices of between 104-107 degrees are forecast for the New Braunfels area today.
The U.S. National Weather Service (NWS) Austin-San Antonio said the combination of warm temperatures and high dewpoints mean elevated heat index values on the first day of the Fourth of July weekend.
The heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature.
Anyone who plans to be outside is urged to drink plenty of water and take frequent breaks from the heat to reduce risk of heat-related illness.
Young children and pet should never be left unattended in vehicles under any circumstances.
Car interiors can reach lethal temperatures in a matter of minutes, NWS said.