The El Nino phenomenon, in which unusually warm ocean currents give rise to abnormal weather conditions, may recur during or before February in waters off Peru, according to the Japan Meteorological Agency.
Since March, the surface temperature of the sea off Peru has been 0.1 to 0.4 degrees higher than usual, it said.
When the five-month moving average deviations of the sea's surface temperature are at least 0.5 degree higher than usual for six months, the agency defines the condition as El Nino, which last occurred from 1997 to 1998.
The five-month moving average deviations measure the average temperature of the month in question and compare it with its four neighboring months.