"Heat gets in the way of your workout performance, In cooler temperatures—anywhere from 40 to 64 degrees—your perceived rate of exertion is lower, which means you can work out harder and sustain your maximal best performance for longer."
Commenting on cold yoga, writer Emily Abbate states: "When you're cold, your body has to use more energy and work harder to maintain your core body temperature (shivering indeed burns calories). Cool environments could help better your sleep quality and can help your alertness—if you've ever tried to sleep without air conditioning in July, you know this is true. Some studies have suggested that exposure to colder temperatures be used as an alternative strategy for exercise, while others go so far as to claim that a lack of cold exposure is a contributing cause of obesity."
For yoga, however, there's a huge downside: when a room is too cold the body is cold and muscles tighten. There can be an enormous risk for injury.
My opinion: traditional yoga is ideal, has passed the test of time, and doesn't need all this contemporary "tinkering". There's too much novelty becoming attached to yoga making it no longer yoga.