Like the atmosphere, the oceans have currents that have an impact on temperature. The currents are like rivers running through the oceans. They usually flow in a curricular pattern. In the Northern Hemisphere, the currents rotate clockwise, and in the Southern Hemisphere they rotate counterclockwise. The movement of the currents helps moderate ocean temperatures. The water moves between the polar and equilateral regions, warming as it moves through the tropics and cooling in the polar regions. Warm ocean currents make nearby coastal regions warmer and cold ocean currents make nearby coastal regions cooler.

England and Kodiak Island, Alaska, are both islands situated at about the same latitude. However, the water currents near Kodiak Island are colder than those that flow near England, so the average temperatures in England are much warmer than those of Kodiak Island.

Sometimes the patterns of ocean currents change a little. When this happens, areas that are usually affected by warmer ocean currents may experience cooler weather and areas that are usually affected by cooler currents may temporarily feel the influence of warmer currents. El Niño and La Niña are examples of changes in ocean currents and the impact of this change on the weather system. Periodically the eastern Pacific Ocean is warmer than usual. The warmer currents bring more rain to many areas; this event is called El Niño. On the other hand, during La Niña the eastern Pacific Ocean temperatures are cooler than normal and many areas receive less rain than usual.