I saw this on another post, i thought i would add some Ideas of my own.
One idea is a flood, it happens in a thunderstorm with a 1% chance, it destroys up to 50 infra and 1 improvement.
Another cool one would be a blizzard, it slows down all resource production temporarily and can destroy up to 60 infra and 1 improvement
Hurricane: It happens in the summer and fall, with a 4% change. Destroys up to 100 infra, and 2 improvements
Hurricane C-1: only in summer: 3% Destroys up to 100 infra and 2 improvements + ts damage
A drought in the summer that reduces food production by 2%
(percents for main disasters are chance to happen in nation)