September can be unpredictable so the answer is I don't know!! Last year for example it was glorious until 7th September when the heavens opened and the temperature dropped for several days. Sometimes it's warm well into October. Even in July and August you can get the odd cloudy day although it never lasts that long. If you have to have hot/beach weather every day then you may think it's not worth the risk and want to look at somewhere further South. Saying that we always find plenty to do if the weather isn't so good - shopping, exploring or just chilling in one of the many bars and tavernas!
