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El Niño extends across the whole equatorial Pacific, a distance equal to 1/3 the distance around the Earth. It is so large that it changes weather around the world, just like moving a heater from one corner of a room to another changes the movement of air in the entire room. The very strong El Niño of 1997-1998 caused:

• severe coastal storms, heavy rainfall, flooding and mud slides in California on the west coast of the United States.
• droughts in Mexico and Central America, which led to forest fires that burned for long periods of time and sent heavy smoke north to the United States.
• droughts in Australia which caused a water shortage.
• unusually mild winters on the east coast of the United States.
• droughts in the mid-west of the United States.
• economic disaster to the Peruvian fisheries.
• ice storms in eastern Canada and New England that caused some areas to be without power for over a month as rain froze on contact with telephone poles, wires, and trees. The weight of the ice caused poles to crumple and wires to break.

The diagram below shows the areas around the world that are strongly influenced by El Niño during winter time in the northern hemisphere (From the National Oceanic and Atmospheric Administration, Pacific Marine Environmental Laboratory).