A rain fly is an extra layer of protection between your tent and the elements. It can be as simple as a waterproof tarp strung from the trees. It can be as complicated as an outer shell designed to fit snugly and attach to your tent for maximum protection in extreme climates. A rain fly guarantees dry sleeping conditions. It is like an outer tent that keeps out the sun, the rain, and the morning dew.
A tent may have waterproof walls. Many, though, are made of ripstop nylon or other material that breathes and is only water-repellent. For full rain protection, these tents require an added rain fly. The rain fly has a waterproof coating.
It’s always a good idea to have a rain fly along. Even if no rain is predicted, the morning dew can be enough to soak your tent.
Rain flies vary in the amount of protection they provide. Types of coverage range from an umbrella to an outer tent.
- Maximum: A rain fly on a wilderness backpacking tent typically extends to the ground. It fits tightly against the tent poles in such a way that there is an air gap between the fly and the tent walls. It attaches at strategic points to the tent structure. This kind of fly can be staked down and will have independent guy lines for further stability.
- Minimum: Campground tents are meant for moderate weather conditions. Their rain flies act as umbrellas over the tent roof. Some are built-in, while others have their own ridge pole and lines.
A stand-alone fly may be used on its own for minimal protection from the elements. A simple rectangle of waterproof material, with grommets or loops along the edges for ropes and poles, can be put up and reconfigured into a variety of shapes.
A rain fly also provides shade. Its waterproof covering breaks down less easily in direct sun than tent fabric. It is always a good idea to keep the rain fly over the tent in direct sun.
Rain flies can act as windbreaks. A stand-alone fly pitched as a lean-to, with one wall facing the wind, provides shelter. Keep in mind that a rain fly by itself does not provide a barrier to insects.
Full-length rain flies serve to conserve heat. They offer warm and dry sleeping conditions in cold, wet weather.