Katrina made landfall over the Florida Keys days before as a tropical storm.
Katrina's track from the Florida Keys to its New Orleans landfall is shown in this satellite photo blending several images with the track superimposed.
Katrina was a Category 5 shortly before landfall. It weakened to a strong Category 3 as it made landfall with at least 80% of the city experiencing Category 1 or 2 level sustained winds. New Orleans was hit with winds of 125 miles per hour. Below is a closeup high resolution satellite photo of the eye before landfall.
The eye over New Orleans
This graphic shows the level of the city compared to the level of the Gulf of Mexico. You can understand why 80% of the city was under water.
It proceeded inland with winds rapidly decreasing as shown below.
High winds were reported as far north as Detroit and Cleveland of over 50 miles per hour.