In the Fall, getting a head start on a morning hike is one of my favorite things. The air is still crisp from the cool evening before, and I love to catch glimpses of the leaves beginning to change colors.
One thing to remember though is you've got to wear layers. Even though it's chilly when you start out, as soon as you get trekking up that mountain, you'll heat up fast. Make sure you have on a tank top under a long sleeve shirt. My favorite to wear is a lightweight Capilene baselayer from Patagonia. It'll give you added warmth if you're cold, and as soon as you warm up and start sweating, it'll wick moisture away from your skin. Then when you get really hot, you can peel this long sleeve off, and either tie it around your waist or shove it in your pack.
Depending on how high you are hiking up, you also want to bring a windbreaker or windproof layer. Even though you may be sweating all the way up, it can be surprisingly windy and cold at the pinnacle. You've worked really hard hiking to the top, so you want to be able to stay and enjoy it without freezing your buns off. I always like to pack my camera, a water bottle, and a LARABAR so I can snap some pics and have a snack.
Fit's Tips: Be sure to wear a pair of wicking socks too. You want to pull moisture away from your sweaty feet to prevent blisters.