The Washington Nationals have a dome stadium due to the fact that the nation's capital experiences extreme weather conditions, such as snow and high temperatures. The stadium's roof is made of a special material that is designed to withstand the wear and tear of extreme weather. The roof also helps to protect the players, fans and staff from the elements, as well as reducing the amount of noise that comes from the crowd. The dome also allows for a longer baseball season, as games can be played year-round. It also provides a more consistent playing experience for players, as the temperature and humidity remain more constant under the dome than they are in open-air stadiums.