Update from NHC a few moments ago:

BECAUSE RITA WILL BE CROSSING AN AREA OF HIGH HEAT
CONTENT DURING THE NEXT 12 TO 24 HOURS...IT IS EXPECTED THAT THE
HURRICANE WILL MAINTAIN ITS STRENGTH. THEREAFTER...THE OCEAN HEAT
CONTENT IS NOT AS HIGH AND THE INTENSITY CHANGES WILL BE CONTROLLED
MAINLY BY EYEWALL REPLACEMENT CYCLES AND DECREASING HEAT CONTENT.
SOME WEAKENING IS ANTICIPATED BUT RITA IS FORECAST TO MAKE LANDFALL
AS A MAJOR HURRICANE...AT LEAST CATEGORY THREE.

A 3 is much better than a 5 - but it's still very prudent to leave the area given the chance for flooding, falling tree limbs and tornados.