I'm going to agree with you guys, I have a shaved head and always have sunscreen in the center console or try to have a hat. Another really important lesson that I have learned when wearing a hat while your driving around without a top. Get a fitted "FlexFit" anything somewhat loose will fly off your head at the first gust of wind. That, or drive around with the hat backwards.
This is what the hat looks like from the inside. The flexfit band is awesome when you have a shaved head, it really does a great job of staying on.
I learned this the hard way as well. Not on my head, but on the side of my face and the neck area... Now I have a spiderwebshade but still put on sun tan lotion if I know I'll be driving in the middle of arizona afternoon.
2013 Commando Green Freedom Edition JKU
2013 Billet Freedom Edition JK
You have to lay down a base. As soon as the weather starts getting nice, get out in the sun. Do some yard work, take a walk. Got to get the tan built up. Takes time, otherwise you burn, then peel, and that looks funky.
This is from experence, I've been taking lunch walks in the spring sun for quite a few years.