In packing for your trip, keep in mind that this is a land of extremes, with an often-unforgiving climate and terrain. Those planning to hike or bike should take more drinking water containers than they think they'll need -- experts recommend at least 1 gallon of water per person per day on the trail -- as well as good-quality sunblock, hats and other protective clothing, and sunglasses with ultraviolet protection.
Summer visitors will want to carry rain gear for the typical afternoon thunderstorms, and jackets or sweaters for cool evenings. Winter visitors will not only want warm parkas and hats, but lighter clothing as well -- the bright sun at midday can make it feel like June.
Take a first-aid kit, of course, and make sure it contains tweezers -- very useful for removing cactus spines from your flesh if you should make the mistake of getting too close. Hikers, especially those planning to go into the Narrows at Zion National Park, will appreciate having a walking stick to brace themselves against the sometimes strong currents on the "trail" that's actually more wading than hiking.
