The other factor in the heat will be how fit everyone's kept themselves. A lot of the England team were playing until fairly recently, but most of those that weren't would have known they were going to get picked and hopefully kept themselves fit. I wouldn't be at all surprised if a couple of the Samoans weren't even aware they were going to play until fairly recently.
I should also add that it won't be 30 degrees at 4 p.m., and it won't be that humid either. We're nowhere near that level of heat yet.
