September is a fine month to cruise. You just need to be aware that you will be cruising during hurricane season and that increases your odds of port schedules being changed or eliminated due to weather. If you can be flexible with your ports of call September will be just fine
Sept. is a good month to cruise, less kids because they are back in school. Only drawback, its till hurricane season and there is always that possibility of bad weather, but have cruised in Sept. a few times and have had beautiful weather.
We cruised last September and I had the same fears you do. It was best weather we've had for sailing. The seas were the calmest I have ever seen.
If a hurricane does pop up, the cruiseline will just avoid that area.
Mary Lou Scanlon
NCL Pride of America April 24, 2010
NCL Epic February 12, 2011
RCCL Allure of the Seas - September 18, 2011
Celebrity Eclipse - February 11, 2012:
RCCL Navigator OTS - February 9, 2013