Covington, LouisianaPeople who live along the low-lying reaches of coastal Louisiana can be surprisingly sanguine about what hurricane season delivers come August. Lesser storms with names like Danny or Gustav sweep ashore and are soon forgotten. On Saturday, residents of New Orleans will observe the 15th anniversary of Katrina—the unforgettable, massive hurricane whose storm surge fed the collapse of the levees but still could not wipe their famously below-sea-level city off the map.

There’s no playbook, though, for fending off powerful hurricanes that hit in the midst of a pandemic—let alone one that arrives where the infection rate surged to one of the highest this summer. Officials guided by more than a century of hurricane preparedness have been forced to rewrite