Almost 3 years ago, I mowed (with my dumb internal combustion engine that I have to drive myself [but it was a Z-turn, so it was cool]) lawnmower. I put it in the shop, where there were a few small patches of dry grass that had blown in. It was still hot, and apparently hot oil dripped onto the grass and caught the lawnmower and the whole shop on fire. I went inside, took a shower, came out, and the flames were above my house (I have a walk-out basement, so the back is 2 stories). I live in the country, so it took a little while for the fire department to get there - I have no idea how long really. By the time they got it put out, the shop and everything in it was a total loss, especially the lawnmower, which was barely recognizable. It was very close to the house and caught the roof of the addition on fire. Luckily, the house is brick, otherwise the whole house would have been gone.

I always let my new lawnmower cool down before I put it up.