One of the best things to do in warm weather is to experience nature up close and personal, especially if you're coming from the big city. If you want to trek up some mountains in Los Angeles or New York, and everywhere in between, AllTrails has you covered. You can choose from over 40,000 different trails, and get reviews from other AllTrails users and write your own. From there, it's all up to you: choose paths for mountain biking, fly fishing, or some other great adventure. The app will keep track of your trail through your phone's GPS as well. Found yourself in LA with nothing to do? Why not take a hike up to the Hollywood sign. Bet you didn't know you could do that, did ya?