Yellowstone National Park
Yellowstone's weather can vary quite a bit, even in a single day. In the summer, daytime highs can exceed 70°F (21°C), only to drop 20 or more degrees when a thunderstorm rolls through. It can snow during any month of the year, and winter lows frequently drop below 0°F (-18°C), especially at night. Bring a range of clothing options, including a warm jacket and rain gear, even in the summer.
Yellowstone National Park covers nearly 3,500 square miles in the northwest corner of Wyoming (3% of the park is in Montana and 1% is in Idaho). Yellowstone has five entrance stations, and several are closed to regular vehicles during winter. It takes many hours to drive between these entrances, so be sure to check the status of roads at the entrance you intend to use while planning your trip and before you arrive.