Before the War
Before the War, Cloudsdale was famous for its weather factory, where Pegasi would hoof-craft snowflakes and manufactured the weather for Equestria at large. The "Best Young Fliers" competition was annually held within the cities cloud coliseum.
During the War
Cloudsdale continued to provide its weather services during the war and sent out Pegasi to the front lines to serve in the war efforts.
After the War
Cloudsdale was completely destroyed and was the first location hit by a megaspell. A few of its citizens managed to evacuate before the megaspell hit, but the most that remained were evaporated nearly instantly along with their floating city from the enormous blast and temperature of the spell. Some ponies such as Ditzy Doo/Derpy Hooves (Or simply even "Derpy") are suspected have been turned into ghouls by the megaspells, managing this by being far enough away from the city and mutating by the fallout. Many other ponies also turned into feral ghouls. A number of feral Pegasi Ghouls were discovered still living 200 years later when Littlepip, Calamity, and Velvet Remedy passed through the region the city once floated above.