I have a campfire burning and I sat there for around 3 minutes. In that time I saw 4 mobs walk straight into the fire. The mobs were...
1 Pig
2 Chickens
1 Sheep
What I expected to happen was for the me and the mobs to catch fire no matter what the weather was.
All you have to do is just make it rain and walk through the fire and you wont burn. For beta only.