The weather is the weather in the Southeast, especially in the spring, summer and hurricane season - not sure where else they can go tbh ... for the most part ... I have more difficulty out of EWR (Newark) when there is a drizzle tbh ...
My point is that the hubs can be in cities not prone to such severe weather.
Delta uses Salt Lake City and Minneapolis as hubs. Neither are prone to severe weather in the peak travel time of summer.
Atlanta is probably the worst place to have a hub. NYC I understand, just from a logistical perspective of travelers moving through there. There should be more hubs in the west, honestly.