If you go to the national weather service website you can get the statistical info in terms of "odds".
It's hurricane season, so obviously there's a chance.
Carnival Elation March 11
Carnival Imagination Sept 07
Carniival Sensation Dec 06
RCI Sovereign of the Seas Sept 06
Carnival Miracle Sept 05
Carnival Glory Sept 04
Carnival Fantasy Jan 04
Late August through early October is the peak of hurricane season. But no one can predict whether you will have any kind of storm. They can't even predict where the storm will go when they know one is out there. Living on the Gulf Coast, I live with the chance of a hurricane striking us every year. We also have beautiful weather in September. The ship will go around a storm though, so don't get scared off by the possibility.
the chances are less the further south and west you go. The eastern Caribbean seems to get hit the most. Its hurricane season so the possiblity always exists.
Your safety is the Captain's main concern, he will steer around the storm, you might miss a port of call or call on another port. If he cannot steer around the storm safely he will find a safe haven and put into port. You might get some rain and some rough seas but that's usually about it.
we did western caribbean last sept 7-14 and had no major problems - there were a couple of huricanes out there but we didn't really feel anything. just be prepared for the fact that a port might get changed just in case. i think the ships do whatever they can to avoid problems, so it might mean missing or changing a port. if you're ok with that, i wouldn't worry at all.