No, it doesn't rain all the time!
Actually, September weather tends to be generally warm with quite a bit of sunshine if you're lucky. However, your luck is far from guaranteed and you would be well advised to bring a light rain jacket and/or an umbrella.
Average September temperature is about 14C with 3.75 hours of sunshine per day. Average rainfall for September is 80mm.
sigops96 @ dsg.cs.tcd.ie>