Your dog needs water as much as you do, maybe more, so carry plenty and offer it to him often. Keep it cool, but not cold. Pay attention to the weather, too. On hot days he'll need more water, just like you. Don't be tempted to let him drink from the gutter or a convenient puddle. Chemical hazards, like antifreeze, can contaminate outdoor water, so take a supply of fresh, clean water for both of you, and don't forget to share.