Seasonal Closures: The park itself is open year-round, but heavy snow restricts access to most of the park during winter months. Icy conditions can last late into June and even July so you'll want to plan your camping trip later in the year. You can check the campground status here. Most are campgrounds are fully operational between June and September. Campsites that are marked as primitive status have no potable water or dump stations available during that time of year.