Consider lightweight waterproof gear: The most suited jackets are the Patagonia Torrentshell, Arc'teryx Zeta SL, and Columbia Watertight. For pants, check out the Outdoor Research Helium or Patagonia Torrentshell Pants. Lightweight ponchos, such as the Sea to Summit Ultra-Sil, are also packed neatly in your bag. Don't forget your pack rain cover, like the Osprey Raincover, and, if you have space, maybe an umbrella or waterproof shoe cover. Lightweight, packable, and keeps you dry!