The runners in Michigan and other states where the usual summer conditions during July and August have been generally absent this year now have to face reality. Hot and humid conditions have returned. :(
It is amazing but true that your runs will be less pleasurable during usual summer heat and humidity. Human physiology reacts negatively to these conditions. Your perceived exertion will rise and actual performance will drop. So basically you will work harder and go slower. Not an appealing combination nor the outcome most of us want from our runs.
So what to do? First, reset your expectations. By adjusting what you want from your run you wont be disappointed and the result from a given run can still be considered positive. Second, prepare you body by hydrating way before you begin your runs. Now would be a good time to follow the industry recommendation of 3 liters for men and 2.2 liters for women each day. Hydrate throughout the day and preceding days. Don't try and get all your hydrating in right before a run. It wont work and it will hinder your run by expanding your abdomen and impeding full breaths.
Lastly, if you are in training for a Fall endurance race, know that slowing down during the hot summer months is not going to have a major impact on a time goal for that race. Keep running through the summer, build muscular endurance and the many other factors needed for a good race outcome, and when the weather cools you can bring speed and performance back into your runs.