Adjust Your Workout for Hot Summer Days

High heat (85+ degrees) + low humidity (under 30%)

The effects: Blood sent to skin to assist with cooling decreases blood supply to working muscles.

The solution: Reduce run by 20 percent, says Joe Puleo, coauthor of Running Anatomy.

Learn how to adjust your workout to the summer heat from those who know—a Miami running club.

High heat (85+) + high humidity (over 60%)

The effects: Raises core temp, reduces blood volume; humidity interferes with evaporation of sweat.

The solution: "Stick to easy runs or use the treadmill," says Puleo.

All fluids are not created equal. Here's what to drink and when.

High humidity (over 60%)

The effects: Decreases effectiveness of cooling system by hampering evaporation of sweat.

The solution: For runs of an hour or less, drop your pace by 30 seconds per mile. For runs over an hour, scale back by 60 seconds.

Exercising in high temperatures means more than hydrating properly. Here's a summertime survival guide.

Heat from ground radiating upward

The effects: Hot surfaces alter microclimate around runner, making it hotter.

The solution: Run on dirt.

"Trails absorb less radiant heat than pavement or a track," says Doug Casa, Ph.D.