Relative humidity readings on the left and temperatures along the top of the chart show the heat index in the center of the chart, with the darker the color, the greater the likelihood of heat disorders with prolonged exposure or strenuous activity. The National Weather Service issued a Heat Advisory Monday, July 4, at 2:08 p.m., expiring Friday, July 8, at midnight, which included Texas and surrounding counties in Missouri. On Tuesday, July 5, at 2:34 a.m., the alert was upgraded to an excessive heat warning through midnight, Thursday, July 7. Dangerously hot conditions and heat index values up to 110 are anticipated. Extreme heat and humidity will significantly increase the potential for heat related illnesses, particularly for those working or participating in outdoor activities.