Crazy Fire Spreads fast even in rain

A fire triggered by Lava was spready like crazy. Turned on the rain which barely slowed it down.
The birch forest was quickly destroyed. I let the rain run for 2 hours the the fire was still spreading. The over generated Jungle is burning even faster. At this rate, without the rain, the entire biome would be destroyed in no time.

Something is really wrong here.

Also noticed in the 3rd image, the frame rate dropped to 6fps. I normally get 60fps or more.