The cooler waters of a La NiÌ±a inhibit cloud growth overhead as seen in this image of the Pacific Ocean on November 8, 2007. A La NiÌ±a event occurs when cooler than normal sea surface temperatures form along the equator in the Pacific Ocean, specifically in the eastern to central Pacific. The La NiÌ±a we are experiencing now has a significant presence in the eastern part of the ocean. The cooler water temperatures associated with La NiÌ±a are caused by an increase in easterly sea surface winds. Under normal conditions these winds force cooler water from below up to the surface of the ocean. When the winds increase in speed, more cold water from below is forced up, cooling the ocean surface.