https://www.bbc.co.uk/sport/football/articles/cp862416n77o
This might only be a bit of a gripe for this tournament as it's not so important, but they need to get to grips with it for the WC.
You can't expect it to be the same conditions as Europe, and the US is having some unusual weather at the moment, but there's every chance a lot of the games are going to played in heat (edit: apparently WC games need to be on real grass), so a bit of trial and error required here. If they throw in a shit match ball like we had in 2010 then it becomes a fractionally more randomised tournament. Maybe FIFA wants that?