The states Katrina impacted were nearly bankrupt though.
Frankly, whenever a category four or a category five hurricane threatens a large city you should be terrified. There is a strong precedent of Presidents flying/drivng/riding down immediately to help with coordination. Nixon, LBJ, Clinton, and Bush Senior all personally went to handle relief for Camile (190 MPH winds) in 1969, Betsy (125 MPH Winds) 1965, Andrew (175 MPH Winds) in 1992, and Clinton famously cancelled a meeting with Chinese leadership for Hurricane Floyd in 1999. Even Bush Jr went to handle the four hurricanes in 2004 - Charlie & Ivan especially.
Overall, I think Bush will be remembered as an exceptionally unlucky president, who was also more incompetent than usual. So if he would have been 4/10 normally, the events he faced knock his administration down to 2/10 or 3/10. Clinton I would say was exceptionally lucky, but also an average president, so he would have been maybe 5/10, and since he was lucky, I could go as high as 6/10.
Not surprisingly, those figures are about where the approval ratings for the Bush Jr/Clinton years ended up. I don't really think Bush was terrible in the second term either, below average sure, but its the first term thats distressing. So its like F/C in my mind. Clinton I'd go C+/B-.
Disclosure: I consider the last presidents in the B or higher range to be Eisenhower (Republican) and Truman (Democrat). Reagan and JFK, the icons of each party, I find highly over-rated.