Hot Yoga originated in the 70s, pioneered by Bikram Yoga. Although most modern yoga studios heat rooms at a certain temperature, hot yoga usually refers to a room heated past 90 degrees (F) with added humidity. Generally, there are two types of hot yoga:

Bikram

• Bikram offers a set of standardized series of poses. Bikram studios generally offer beginner postures classes, which consist of 26 poses. Bikram Yoga is not considered a flow or Vinyasa class, meaning there are no transitionary movement in between poses. Rather, it is a Hatha class, wherein you get into the pose, hold, release, and then move on to the next pose. 
• Heat Level: 95-108 Degrees (F) at 40% humidity. 
• Classes lasts for 90 minutes 
• Bikram classes are offered exclusively in Bikram studios by Bikram-trained teachers. 

Vinyasa Heated Yoga: Less Rigid with Variety 

• Unlike Bikram, Vinyasa heated yoga classes are offered in various studios. The main difference is the lack of a rigid class sequence, so each class is different depending on the instructor/studio. These classes generally take the traditional Vinyasa flow format, which means the incorporation of transitory movements between poses. Several yoga studios offer Vinyasa heated classes, but the most popular franchise is Corepower Yoga and their C2 class. C2 classes maintain a heat level of 95-98 Degrees (F)  and humidity varies. These classes are usually 60 minutes long.