GENEVA (Reuters) - El Nino weather conditions associated with droughts and flooding have a 50-60 percent probability of developing by May this year, the U.N. World Meteorological Organization (WMO) said on Tuesday, but any El Nino was not expected to be strong.

“WMO recently confirmed 2015, 2016, 2017 and 2018 as the four warmest years on record. But even a weak El Niño is likely to make 2019 warmer than 2018,” Maxx Dilley, director of WMO’s Climate Prediction and Adaptation branch, said in a statement.

A strong El Nino event is defined by sea surface temperatures in the east-central tropical Pacific rising to at least 1.5 degrees Celsius above average. The WMO said it could practically rule out the chance of a “La Nina” event - the cooling counterpart to El Nino.