We have been following it for a couple years now and honestly it has only slightly altered our plans a handful of times. WBGT is NOT the outside Temperature - it factors in a bunch of things, so at first glance it looks pretty restrictive but it hasn't been to bad for us. (Central, Tx)

Take a look at what WBGT really is and plan some extra water breaks and a cooling zone and it will be "just what you do" before long.

At the end of the day it is a safer environment for kids, and while I can definitely argue its a bit extreme than what I think is necessary, it has not really messed with us much.