This in turn means that farms in Chihuahua are under far more pressure to increase productivity to the level of their US peers than are the more geographically insulated farms of southern Mexico. Due to significant variability in elevation across the state there are considerable variations in temperature and the length of growing season. In particular, higher elevations offer opportunities to produce crops, such as apples, that would normally not be expected to be found at latitudes this far South. While agriculture in the majority of the state is not limited by the length of the growing season, virtually the entire state faces limitations caused by low levels of precipitation. This makes irrigation necessary for virtually all forms of arable agriculture.