Which of the USA’s national parks are at their best in summer? Not all of them. Some get overcrowded and others get overheated (or overcrowded and overheated). If you're looking to avoid the first problem, we've gathered some of the lesser-known parks—places that never get crowded, even in high season, and remain comfortable, weather-wise, despite the calendar. But we’re not neglecting all of the popular and steamy options.