We've done it 3 or 4 times now and the weather has been really variable. We certainly have not had two weeks of warm weather. Mixed, is probably the word. We've had really warm days, followed by some cold days. Generally the heat is concentrated between about 10 or 11 am through to about 4pm. Outside of those times, it hasn't been great.

Having said that, it's still shorts and T shirts, with an occasional jumper day needed. If you're doing the parks, it's much better than the blistering heat of August (just don't make the mistake of getting soaked late in the day on a water ride, because you won't dry out.