A powerful storm fueled by El Niño was set to bring rain to California and the Southwest this Halloween weekend, according to a Fox Weather forecast issued Thursday. The system is expected to move east next week, bringing heavy rain, severe storms and mountain snow to 35 states.

Southern California could see moderate to heavy rain by Saturday, likely disrupting Halloween plans in cities such as Los Angeles and San Diego, Fox Weather reports. San Diego has had only nine Halloweens with measurable rain since 1850, the last in 1987.

A major flood event is expected across the Southwest from Sunday into early Monday, the outlet reports. Up to 5 inches of rain could fall from Phoenix to Flagstaff. On Sunday, a Level 3 of 4 risk of excessive rainfall will cover more than 65,000 square miles and more than 4 million people.

Some areas are still recovering from flash flooding last week that killed two people in New Mexico, Fox Weather reports. Rivers could again rise close to last week's levels. In the mountains, the southern Rockies could get 12 to 18 inches of snow.

Later Monday, the storm is set to move into the Plains and Midwest. Nearly 40 million people are under a Level 1 of 4 flash flood threat from Texas to Wisconsin on Monday, the outlet reports.

Severe storms could form from Monday into Wednesday, from Texas into parts of the Southeast. On Election Day, rain could fall across the whole central part of the country, Fox Weather says.

What we know: A large storm is set to bring rain, floods and snow from the West to the South over several days.
What we don't: How the forecast has changed since Thursday. Only Fox Weather has reported this so far, and NewsHabit hasn't seen independent confirmation.