The ENSO phenomenon, which stands for El Niño/Southern Oscillation, involves the fluctuation between El Niño and La Niña episodes. It has been shown to have a dramatic effect on the weather of locations worldwide. This air-sea interaction over the Tropical Pacific alters atmospheric wave patterns, thereby changing the movement of storm tracks, which modifies normal weather conditions. This study will explore the effects of the 1983-'84 and 1998-'99 La Niña's on fourteen U.S. cities to determine the impact of La Niña on temperature and precipitation patterns across the nation. Climatological monthly averages for each of the cities will be compared with the data from these two La Niña events as well as with each event's respective 30-year normals. This comparison and analysis will help determine the relative strength of these La Niña events and the magnitude of change they induced on normal weather conditions throughout the country. This study will also examine if there is a correlation between the magnitude of preceding El Niño episodes and the following La Niña events.