See 5 of the worst droughts in the United States

The ongoing drought in the United States has ties to La Nina, National Oceanic and Atmospheric Administration meteorologists say. La Nina is a weather pattern that consists of an abnormal cooling of the Pacific Ocean that brings dry conditions to the southwestern United States and Mexico. La Nina has been linked to the Dust Bowl of the 1930s, the dry spells in the Southwest of the 1950s and the drought from 1998-2002. See 5 of the worst droughts in the United States.