An optimal down-filled jacket with zip-front closure. Wear it whole or zip away the sleeves to reveal a vest. No rain or wind? Zip off the hood for more head room. Dual-zippered side pockets are there to hold your stuff, no matter what.
Have water with you at all times. An incognito 100-ounce hydration reservoir nests inside a hidden rear zipper pocket, with a leakproof cap and hidden drinking tube that leads up to your shoulder. Have a sip. Stay hydrated. Repeat.