The latest long-term forecast shows the chances of a wet El Niño weather pattern bringing drought relief to California starting this fall has decreased to about 65%, and if it does arrive it will probably be weaker than originally expected.
If an El Niño does develop, it should emerge by October and peak during late fall and early winter, according to the Climate Prediction Center and the International Research Institute for Climate and Society.
Forecasters previously put the chances of an El Niño forming during the same period at 80%.
Higher-than-average sea surface temperatures continued in the eastern equatorial Pacific during July, forecasters say.
The strongest El Niño events in California occurred in 1983 to 1984 and 1993 to 1994, Paul Iniguez, science and operations officer for the National Weather Service in Hanford, Calif., said last week.
In a weak to moderate El Niño, he said weather conditions are unpredictable and a "mixed bag."