I am right there along with you...I am sick of it! But I have managed to continue riding. Although, I have been experiencing the early signs of heat illness (high heart rate, chills, dizziness). It took me a few rides to figure out what was going on, but I eventually did. I could not understand why, besides the obvious heat, my heart rate was so high on my rides. And I noticed this started right after I began taking a certain medication. I wear a heart rate monitor, and I could not stay out of zone 3 and 4 at a fairly easy-moderate pace. And I would get chills towards the end of my rides. Then last Saturday, I rode that morning and finished by 11 am. I was still getting chills and it was not that hot yet (low 90s?). But I did notice I had not urinated the entire 47 miles, and when I finally did, it was a yellow-brown. Again, it was not making sense to me because I drink more water than most riders I know, before-during-after the rides. On the rides, I supplement my camelback with pure electrolyte powder, and I keep an electrolyte-carb drink in my polar bottles. So I did some research online this week, and found this Sports Medicine journal article about certain groups of people who are vulnerable to heat illness, and bingo, my type of medication was listed in that article. Apparently, the meds are making me dehydrated, and what would normally be enough water/day for a Texas summer is not nearly enough. Also, the article suggested that even during prehydration you should supplement the water with electrolytes-sugar. So Tuesday I drank at least 5 liters of water, and alternated it with electrolytes and sugar. Then on my ride after work, it was 104 degrees and high humidity, and my heart rate stayed down and no chills. I was so happy I figured it out!

Everything HappyTexasMom suggested I second. The only thing I would add is prehydration. With consecutive 100 degree days prehydration is extremely important. We cannot drink enough these days, and do not be afraid to use some electrolytes and sugar pre-ride. The two products I like are the Hammer Endurolytes powder for just electrolytes, and the Luna Sport Electrolyte Splash drink mix for electrolytes+sugar. It is low on the sugar, and has vitamins and minerals.

Good luck!