Joan Fessler has a pretty good idea how she must look. It’s one of the most oppressively hot and humid days of the year. And she’s in a room where the heat is cranked up to 105 degrees. On purpose.

“Crazy?” guesses the Towson, Md., preschool teacher.

While everyone else is searching for ways to cool off, devotees of “hot yoga” spend 90 minutes sweating through a series of stretches and poses in a room designed to be even hotter than Baltimore in the summer.

“It’s difficult to explain. … You’re so at peace. It’s well worth the suffering,” Fessler, 52, said after a recent workout at Bikram Yoga Baltimore, a studio in Cockeysville, Md.

Actually, she and others say, Bikram yoga helps them cope with sweltering summer days.

“When it’s 95 degrees outside, you’re just thanking God you’re not in triangle pose,” says Eddie Garner, who owns the studio with his wife, Emily.

The summer heat might not be breaking records, but it is enough for Baltimore to declare a Code Red and open six cooling centers. In Baltimore County, officials are monitoring the weather and calls for emergency medical services for heat exposure and troubled breathing.

The stretch of days in the 90s toward the end of July may have felt worse than it is because the summer has been relatively mild in comparison, officials said.

In the Cockeysville yoga studio, instructors control the temperature and keep the humidity level in the 30 percent to 40 percent range, which is ideal for Bikram yoga, a series of 26 postures and two breathing exercises done over 90 minutes.

About 20 people attended a recent noon class. They wore shorts and tank tops, with no socks or shoes, standing on what look like beach towels.

Within the first few minutes, everyone is sweating. It starts as beads of perspiration on foreheads. But most of them are drenched in sweat by the time the class members twist their arms and legs into the “eagle” pose.

“Exhale,” instructor Kyle Kessenich reminds them.

Although it is known for being challenging, the Bikram style, named for its founder, Bikram Choudhury, an Indian yoga master and businessman, is helpful to those with joint problems and back pain, Emily Garner says.

The studio in Cockeysville offers four to five classes daily, with about 25 to 30 people in a typical class.

Attendance falls off slightly in the summer, but mostly because of vacations, not because people avoid yoga class on hot days, Eddie Garner says.

“This kind of sweating is cleansing,” he says. “Your body starts to crave it.”

However, the owners do see a slight increase in attendance during really cold snaps, when the thought of trying hot yoga seems more universally appealing.

“It’s easier to go in a room and pretend you’re in Bermuda in January,” Emily Garner says.

Sun reporter Brent Jones contributed to this article.