Most of these completely write themselves, and would make very compelling historical events as well as be an important consideration for fort placement. I'm imagining that these events would be quite rare, and would have a wide degree of severity. Some of these are mega-fps-death-crash causing ideas though
There are a lot of things in place already which would lend very well to natural disasters, especially the detailed geology that Toady is so fond of.
Earthquakes: At world gen add hidden faultlines and earthquake hotspots. If a fort is built along a faultline, depending on the severity of the quake, its possible that the fort will be torn in half. Additionally earthquakes depending on the severity would throw objects around, and have a chance to collapse tunnels, what a nightmare.
Tornado: Pick up items, creatures, and constructed buildings.
Eruption: for our powergamers
Thunderstorm: chance to strike a creature 95% fatal, 5% chance to obtain severe burns but legendary in a random skill. Chance to cause a
Wildfire: depending on the availability of flammable life, perhaps even grasses would burn.
Flood: limited more to flood planes, deltas and valleys
Heatwave: Limited to warm, hot, and scorching areas reference:
https://www.youtube.com/watch?v=98I5LTPcRnw Drought: all natural water sources reduce in degree, heavy aquifer-light aquifer, stream-brook
Blizzard:Add snow/ ice tiles covering the map
Hailstorm: damage creatures exposed to weather
Locust swarm: eats food and attacks exposed dwarves.
There's a lot of potential as well in some of the DF specific biomes, like an errant evil cloud near an evil biome, or some good biome related disaster like livestock being turned into fairies.
Before you say it will never happen, imagine the
!!FUN!!+