I bet not even Europe or China can figure out how to suddenly house/feed a million people who had to evacuate from a city for a few days, or even overnight.

Evacuation are very different from attending work, or attending a festival. Namely... You plan to return to your home/apartment/etc. and your belongs will still be present. There isn't the threat of death.

Furthermore Evacuations require moving people who often _don't_ have the ability to travel on their own. Rather by choice, or socio-economic pressures i.e.: poverty, or limited parking in city centers. Therefore attendance to work/events for these people is normally just walking a handful of blocks, or using public transit which become limited when dealing with evacuations.