Training in an oven

At 5:00 p.m. here in Houston, the current temperature is 91, the heat index is 101, the humidity is 60% and the winds are blowing out of the SSE at 13 mph and gusting to 21 mph. It will be at least 10:00 tonight before the heat index falls back under 95 (about 2 hours after sunset). This morning when I went to go swim at 6:00 a.m., almost a good hour before the sun comes up, the temperature was 80 with a heat index of 85 and the humdity was 97%, AND IT'S NOT EVEN SUMMER YET!