WASHINGTON — The El Niño effect is about to hit U.S. weather, but it is not the primary cause of the ferocious storms that brought death and flooding to much of the South over the weekend, scientists said Monday.

However, El Niño could bring temporary relief to Midwesterners plagued by the violent weather. It is predicted to cause a relatively dry winter from the Ohio Valley to the Mississippi River Valley, said Nicholas A. Bond, the Washington state climatologist and a senior researcher at the Joint Institute for the Study of Atmosphere and Ocean at the University of Washington.

“It is just sort of a fluke event,” Bond said of the weekend storms that brought tornadoes and violent storms at a time when people normally hope for a white Christmase.

“Sometimes you can get these big troughs of lower pressure and ridges of higher pressure that set up in particular places and stay there and end up steering the storms different than they usually are for this time of the year.

“There is just randomness in the weather that is always there,” he said. “And impossible, really, to predict with much lead time.”

Missouri State Climatologist Pat Guinan agreed, but said even with the dry forecast, winter’s short days, cold temperatures and dormant plants are not conducive to evaporation.

“We are not going to dry out anytime soon regardless of what happens over the next few weeks,” he said.

While much-needed precipitation is forecast for the American Southwest from California to Texas, an El Niño effect about to kick in on North America will bring relief from saturated grounds elsewhere, according to the latest government forecast.

“Seasonal outlooks indicate an increased likelihood of above-median precipitation across the southern tier of the United States, and below-median precipitation over the northern tier of the United States,” the National Oceanic and Atmospheric Administration said in a mid-December El Nino report.

“In terms of dryness, it is kind of the Ohio Valley extending to the Mississippi, including the St. Louis area,” Bond said.