Acknowledging the weather would be start, they don't even need to acknowledge climate change. Just realize that when it's over 98 degrees and you plan on a full day of hiking in the wilderness...
Bring a bunch of water and take plenty of breaks in the shade.
Just make informed choices. Want to visit Death Valley! That’s great! It’s a beautiful park worth seeing. But don’t go in the middle of summer, go in fall or winter when the daytime peak temperatures will be much more comfortable.
If you MUST go in the summer, plan ahead. Bring several gallons of water with you per person, plenty of sunscreen, ideally a hat and sunglasses, and lightweight, breathable clothing that won’t trap your sweat and body heat. And on top of that, make sure your car is up to date with maintenance and can comfortably drive when the temperature outside is 110+. To have all bases covered, it would also be worth investing in a satellite phone- not all national parks have cellular coverage. In my experience, cell service is extremely spotty to non-existent inside of national parks.
I think education is important. I think they should force everyone to watch a 10 minute movie about how people die in parks. Make is very graphic to drive the point home. Like those drivers education movies.