What is the weather like in Mauritius in September?

September is one of the better times in Mauritius weather-wise, not too cold, not too hot.
The real hot season starts in November until Feb/March, and the coldest season is in July and August.
September has temperatures of about 25-28 degrees celcius
(75-80 degrees farenheit), slightly cooler at night. There is pretty much no possibility of cyclones in Sept. Any severe cyclones usually occur in latter Dec. through Feb. (during mid-summer).
Sometimes there are mild cyclones a little earlier or later in the year, but Sept. is too early.
In spite of the temperature being ideal in Sept., this is not the best month to go to see the beauty of the islands. Since winter is July and August in Mauritius, many of the plants are rather dormant and don't flower that much during that time. In September they are starting to come back, but are not really in full-bloom. That is to say that things are much greener, much prettier from November through June.

hold on ill just look into my crystal ball........

Bloody hot.

Probably GORGEOUS and I want to go...................... Now!!!

September in Mauritius is like summer in most northern countries. As it's a small island, you quite often get a nice breeze off the coast. Last time I went, I went in the middle of their winter (i.e. June-July) and found the weather to be like UK summer - i.e. nice and warm-hot with a bit of rain now and again.

it can rain a bit in sept

It can be quite rainy and temps are only about what you'd expect in summer in a temperate zone. The best time to go is in April where it's hot without being too hot and there's not as much chance of cyclones.