The Yellowstone is one of the most remarkable places on the planet. It's home to North America's most iconic wildlife and every year these animals must survive The Thaw - one of the harshest seasonal changes on Earth.
Temperatures swing from minus 40 Celsius in the winter to approaching 40 plus in the summer months.
To understand how the animals cope and to witness the effects of our changing climate, this BBC Two three-part series, stripped across one week, follows the Thaw during 2016, a year when it's believed the unpredictable weather broke new records.
Presenters Kate Humble and Patrick Ayree are joined by a team of scientists and wildlife cameramen. They capture the wildlife dramas as they unfold and analyse the impact on individual animal families of wolves, grizzly bears, beavers and great grey owls.