Vacation conditions in the Cayman Islands in September do not differ from the summer time. There is still the same heat reaching +30°C, regular tropical showers, and sometimes there are hurricanes and storms.
Storms during a Cayman Islands vacation are perhaps even more frequent in the fall than in the summer. Therefore, many yacht trips are canceled, as well as diving on the submarine "Atlantis". However, the water is very warm at this time, so it is quite possible to organize a beach tour to the Cayman Islands in September, if you keep a close eye on the weather.
Prices for vacation in the Cayman Islands in September are not yet starting to grow significantly. The average price for a tour to the Cayman Islands in September is 1600 USD. tripmydream will help you find the best Cayman Islands tour for you in fall.