Summers often bring afternoon thunderstorms, and lightning storms are common. The mild temperatures make it ideal for touring Grand Teton’s higher elevations. Average summer daytime temperatures range in the 70s with lows at nights in the upper 30s and lower 40s. When hiking and backpacking, you can wear shorts or leggings (up to your discretion). Mornings are chilly and can quickly become warm when the sun is present. Evenings can get chilly quickly once the sun goes down, especially in higher elevations.