Climate is the characteristic condition of the atmosphere in a particular region. The Koppen climate classification system identifies five major climate types present in Nuevo Leon, Mexico. The majority of Nuevo Leon (68%) has a semiarid or dry climate with little rain and large daily temperature fluctuations. Temperate climates exist in mountainous areas and account for 7.1% of the state, while very dry and arid climates each cover around 5% of the state. The arid regions experience hot days and warm nights with annual rainfall under 600mm, supporting only small trees, shrubs, cacti and sparse vegetation near rivers.