Hand warmers can be a game-changer when you’re heading out into chilly temperatures. Once, while visiting the infamous snow monkeys in Japan , my fingers got so cold that they wouldn’t register on my phone’s touch screen. Without gloves or hand warmers, I ended up leaving early to warm my frozen digits with a cup of hot tea. Trust me, having to leave an epic experience—or needlessly suffering through it—because of cold temperatures will quickly ruin your day. Whether you’re looking for a temporary on-demand heat source or need to keep nimble during a cross-country ski outing , hand warmers are always a good idea. We personally tested a variety of hand warmers, from compact devices to heated gloves , to find the warmest option for every traveler. Top Picks Why We Love It These all-natural hand warmers are the perfect size to keep on hand just in case, and can be activated on demand for up to 10 hours of warmth.…