I contacted Mountain Campsite in Flagstaff, and they are still closed (due to renewals) and also warn me for snow and bad weather in April? They said it would probably be too cold to swim the sliderock park anyway.
I kind of got confused there, as we choose the southern states to stay away from bad weather and have decent temperatures :o. If I look online at average temperatures for april, they are more then OK (to Belgian standards everything above 20°C is considered hot :D).
I assume I am correct that the temperature generally will be OK? I don't mind a few days of bad weather, it happens and you can't escape it, but in general I am assuming we will be able to spend our days outside without warm jackets and heating?