Hi Jenny,
The weather is always hard to predict but generally September is lovely - it gets a little thundery towards the end of August /early Sept after all the intense heat of the summer, and by 20th Sept its usually a little cooler than August but still lovely tempertures - probabably still in the high 20's Centigrade.
Its a lovely time to go - the visitors at that time are usually couples, or families with one or two preschool children. Everything is still open and there are still plenty of people about so its not too quiet. Its a super time to go, so you should really enjoy it.

thanks. so its still tanning weather then? And still warm at night? we are a young couple so we just dont want it too quiet. we cant go till that late coz we are wanting to go in a villa and earlier is too expensive

Yes, defininetly tanning weather, and it should still be warm enough in the evenings to go out without having to carry a sweater etc.

Went in sept 03, just the two of us. Was beautiful weather. It was kid free, which was excellent! And still v busy. I remember that holiday well, some good clubs and bars there, you will love it. I'm going there for 16 days in july, wish I was goin in sept so I wouldn't have to put up with screaming kids, but alas due to work commitments I can't.

We were in Cala Dor last year for 10 days from the 13th Sept, plenty hot enough. Take your lotion.

Sunburnt.