Rain in August is usually not a problem here; in fact, the lack is usually the issue. But in the last 18 months, there's been an earthquake (while I was presenting at MAC about disasters!), a hurricane, an ice storm, and a July without a single 90 degree day, none of which are typical.
Unlike most floods, the waters didn't rise, we had 5" of rain in an hour (a record, with more rain following), and nowhere for it to go but downhill, which is where the main library is. Luckily, the 'ville is big enough to have branches, so it's not a complete loss, nor did the water reach the first floor. It did take out processing, the server, and the bookmobiles, plus books and pcs headed to the new branch which opens next week.
Always have a hot server, even if it just backs up the home page with an announcement. Keep your server at one of the higher branches, not in the basement of the library that's flooded before.
Have your ducks in a row before you need them. 20 buildings at U of L flooded, plus homes and businesses - fans and pumps are at a premium.
Avoid combined waste and storm sewer systems. Nuff said. Yuck.
Don't put your hvac in the basement. Imagine 4 floors of books, 95 degrees, 95% humidity outside, and 100% inside, with no hvac. My hopes for recovery are low, unfortunately; and insurance is slow.
Don't ever assume it can't happen here. It can.