Predicting El Niño vs. La Niña vs. neutral: relatively reliable.
Predicting how strong the El Niño will be: harder.
Predicting exactly what it will do to rainfall, temperatures, storms, or snowfall: substantially less reliable.
And yet people will put forth dire predictions (drought, flooding, hurricanes, tornadoes, heat waves, etc.) every chance they get. No wonder so many people think it is all a hoax.
Yes, scientists have put forth dire predictions of extreme weather. Here's the thhing though - we actually see measurable increases in the frequency and severity of extreme weather events. They put forth dire predictions.. and they are absolutely correct. It's right there in the observational record.