With all due respect to everybody who was in any way affected by the hurricane, the states have never amended the much-neglected Constitution to authorize Congress to tax and spend for relief purposes associated with natural disasters. But I think that such an amendment would be appropriate.
In other words
Socialize acts of God.
The Constitutional question is a close call, I think. I just did some quick Google research on the history of Federal disaster relief bills, and it appears that the first one was passed in 1803, to provide relief to Portsmouth, NH following a massive fire. Certainly an argument can be made that if Congress in 1803 (which, I believe, included at least a few people who signed the Constitution) thought that such a bill was Constitutional (perhaps because it was "necessary and proper" to help rebuild Portsmouth in order to carry out some other power of the Federal government) implies that similar bills today are likewise Constitutional.
The thing people often forget about the Constitution is that it was the product of significant compromises between opposing factions, and that even at the time it was ratified, there was significant debate as to what the powers Federal government did and did not have. Look at McCulloch v. Maryland and the debate over the creation of a national bank, for just one example.