The eastern parts of the Pacific could be in for wetter weather while the western region could face droughts if the predicted return of El Nino occurs.
A New Zealand scientist with the National Institute for Water and Atmospheric Research says there is a significant chance it will form by the end of the year.
Jim Renwick, who is a senior climate scientist, says he's backing U.S. predictions that El Nino is likely to return.
He says it could have the same effect as it did in 2002.
"Places like Kiribati get a lot wetter than they normally are - it can be two or three times normal rainfall plus the northern Cook Islands and parts of French Polynesia can become a lot wetter than they normally are. Also tropical cyclones tend to travel farther east so the risk of tropical cyclones increases."
Mr Renwick says while the east becomes wetter, places like Solomon Islands and Papua New Guinea will be drier.