This. ^^^

Just did a metric century yesterday and ended up doing switchbacks on a 10% grade for about .25 mi. Not too bad as it was rural and only a couple of cars went by. Make sure you take dog protection as one can't freewheel, unclip and kick at the little(or big ) harrasser on a fg. If you've got one wear a 'road jersey' and keep water bottles and Clif bars in the extra pockets.

+1 on all the other suggestions re food and hydration. It topped out @ 99F on my ride yesterday. Very little shade, so I stopped a couple of times that I wouldn't have normally. Killed 2 glasses of self-mixed Gatorade w/ice when I got home.

Oh yeah, have fun!