A heat wave thawed Siberia's tundra. Now, it's on fire.

For months, Siberia has been experiencing extreme heat due to a combination of persistent sunny weather and human-caused climate change. In addition to producing Arctic temperatures that cracked 100 degrees in June, the heat has fueled an enormous outbreak of wildfires, including fires on tundra underpinned by permafrost—normally frigid soil that is likely becoming even less frozen this year.