The Brief North Texas faces its hottest temperatures of the season this week, with highs near 104 and heat indices reaching up to 112. According to the National Weather Service, most of Dallas-Fort Worth is under an Extreme Heat Warning through 8 p.m. on Tuesday. Symptoms of Heat-Related IllnessTemperatures this week can be dangerous, especially if you don’t know the signs of heat exhaustion and heat stroke. The symptoms of heat exhaustion include dizziness, thirst, heavy sweating, nausea, and weakness. Heat exhaustion can lead to heat stroke.