I'll echo what many have already said, if you're riding 40 comfortably, 62 shouldn't be too bad. Again be sure to stay well hydrated and refuel!! Eat and drink long before you think you're thirsty or hungry especially in the heat. If you have access to cool refreshment at the rest stops, drink or eat them, it helps to cool your core and makes it easier to go on. If you get too warm, don't be afraid to put layer ice in a bandana under your helmet. It cools you gradually and depending on the humidity, it will dry eventually as you ride. I've also been known if it was absolutely horrid, to put ice in my bra to cool me off. The key will be the hydration and nutrition though.
I rode a metric just weeks after I started riding in 2005 but I'm insane If I'd realized what I was doing, it might not have happened that way LOL.. I'm taking it easier this time around and trying to gradually build my rides back up.