system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is the Fort McMurray fire uncontrollable?
gpt
It is just after winter, so nothing was really green yet (evergreens still are green, but haven't come out of dormant state yet). That means everything is still dry. It is really hot, 30°C (unusual for early may). The relative humidity was low. And high winds make the fire move quickly.

Forest fires happen a lot. It is just that this one happened to be near a large city, which are very rare in northern Alberta.