Updated May 18, 2015.

If you sign up for hot yoga, just how hot will it be? The answer depends a lot on the specific type of yoga that you are trying. Anyone can offer a hot yoga class just by cranking up their heater, so there's not always a standard temperature, though most aim for between 90 and 105 degrees Fahrenheit. Also keep in mind that all heat is not created equal. Some hot studios have state of the art radiant heat, while others throw around a few space heaters and call it good.

Some also control the humidity of the room, making for an even sweatier experience. Each of these factors will affect how hot the room actually feels. Before trying hot yoga, or any yoga for that matter, it's a good idea of check with your health care provider to make sure that it's an appropriate activity for you. And make sure to drink water! Here is a heat index for some of the most popular hot styles.

Bikram

The most well-known kind of hot yoga is Bikram, in which the studios are heated to 105 degrees Fahrenheit and 40% humidity. Bikram yoga is defined by a 26-pose series, which is always done in the same order. Classes that imitate Bikram's sequence (and are prepared to be sued for it) will also turn up the heat to around 105.

Yoga to the People

This rapidly expanding chain of donation studios with locations on the east and west coasts famously settled Bikram's copyright infringement suit out of court, agreeing to stop teaching Bikram's series. Yoga to the People studios now offer Traditional Hot Yoga classes at 105-108 degrees F.

CorePower Yoga

This popular chain of studios has a lot of different classes on their menu, each with its own preferred temperature. The CorePower Yoga 2 (C2) class, which is their all-levels hot flow class, is taught in a room maintained between 93 and 98 degrees F. Their Hot Yoga is 26 poses in a 105 degree room (sound familiar?).

Baptiste Power Vinyasa

Headquartered in Boston with affiliated studios in more than 20 other U.S. states, Baptiste Power Vinyasa studios teach hot flow yoga in the style of Baron Baptiste. Classrooms are heated to about 95 degrees F.

Moksha Yoga/Modo Yoga

This Canadian-based yoga franchise with locations in five U.S. states (and counting) keeps their "green" classrooms at 103 degrees F. The Moksha sequence is always the same 40 poses, which takes about 90 minutes. Students who are short on time can take a condensed 60 or 75 minute version of the sequence, while those who like vinyasa can try the flow version.

Evolation Yoga

This rapidly expanding style boasts studios in the U.S., South America, and Australia, with additional affiliates in Europe and Asia. Co-founder Mark Drost was once a senior Bikram instructor. Evolation teaches Bikram's sequence under the moniker Primary Hot Series (you may remember the associated copyright suit) at 105 degrees. Their other offerings range in temperature from 75 to 90 degrees.  

Sunstone Yoga

With 12 locations in Texas, this franchise offers a range of hot yoga and even hot pilates. Their signature hot yoga class is done at 98.6 degrees F and 60% humidity. They also offer quite a few classes at a more modest 90 degrees.