Summer months are a great time to get outdoors and stay active with a brisk walk or fun run.

But the extra daylight hours come with added heat as temperatures approach the low to mid 90s and sometimes higher. Factor in a little thing called the heat index, and it could spell trouble if you aren’t prepared properly.

According to the National Oceanic and Atmospheric Administration, the heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature.

For example, on a day in which the temperature is 92 degrees with a relative humid of 85 percent, the heat index means your body will feel the apparent temperature of 126 degrees Fahrenheit — which is pretty darn hot.

Josh Maxwell formed the Liberty Run Group about seven years ago. The group has about 30 active runners, ranging from beginner to advanced. Maxwell said that during the summer months, walkers and runners need to learn to adjust their workout schedules and water intake to beat the heat.

“The biggest thing is hydration,” he said noting that it is fairly uncommon to experience a heat-related illness during colder and moderate temperatures. “But in the summer, especially here in the South, where it is humid and hot, … it makes it very important to stay hydrated. I always tell my runners to take in water all day throughout the day.”

Maxwell cautioned that taking in too much water shortly before a run is not the best either. He said it could leave you bloated and without the benefits of the water being absorbed into the bloodstream quickly enough to protect your body from the heat. The same can be said for sports drinks. Those can and often do provide a few benefits if consumed properly.

Active.com says water works just fine for workouts shorter than 45 minutes. For longer runs, the website reports that research suggests consuming about a cup of sports drink every 15-20 minutes to fuel your muscles and maintain the body’s electrolyte levels.

Maxwell said his group always checks the heat index before starting a run. He said there are a variety of cellphone applications or heat-index calculators available online.

“You to plug in the current temperature and current humidity, and it will let you know what the heat index is,” he explained. “And about all the indexes are broken up into four separate colors — yellow, dark yellow, orange and then red.”

Maxwell said beginners should never push a run when the heat index is in the dark orange or red. Experienced runners, he said, should gauge how they feel and modify their running by rescheduling their start time or running in the shade as often as possible.

“It helps a little,” he said of finding a shady spot in which to run. “And every summer, we change our run time. … During the summer, we start our runs a half-hour later than we do the rest of the year. … We start at 6:30 p.m. … The reason for that is that half-hour allows for the sun to go down a bit and make it a bit more cooler, and that makes a big impact when you are trying to get some miles in. And we opened our morning group again, and they run at 6:30 a.m.”

Maxwell said he has seen people as early as 5 a.m. out and about, getting their workout routine completed while the temperatures are still moderate.

“They are getting out there and getting it done,” he said.

Runner’s World magazine and Active.com recommend that people avoid walking or running between noon and 3 p.m. Both also recommend walking or running indoors, such as on a treadmill, on days when the heat index is extreme and the outdoor air quality poor, such as on smoggy mornings out West.

Maxwell said runners should wear comfortable clothing, but spending hundreds of dollars on fancy running shirts and shorts are not necessary.

“It doesn’t matter if you buy one of those fancy keep-dry shirts,” he said. “When the sun is out and you are running, you are going to be hot and miserable … unless you are the type of person who experiences that runner’s high when you are dripping sweat and have the sun beating down on you, you are going to be a little uncomfortable. … Those fancy shirts are nice, but you are still going to be hot.”

If you are going to drop big bucks, then Maxwell suggests you spend your money on the truly important items.

“Save that money for the shoes,” he said, “and for the women, a running bra as well.”

Finally, Maxwell said runners should learn to listen to their bodies.

“It will tell you what you need to know,” he said.