A tornado that killed six people in northwestern Oklahoma traveled about 31 miles and had winds of 136 to 165 mph at its peak.
The National Weather Service on Monday assigned a preliminary EF-3 Enhanced Fujita scale rating to the storm after conducting damage surveys.
Forecasters say the tornado developed about 11:50 p.m. Saturday near Arnett in Ellis County and damaged six structures.
Once the storm reached neighboring Woodward County, it downed trees and power lines before hitting two mobile homes and killing three people.
When it crossed into southwest Woodward, the storm damaged homes and businesses as it tracked to the northeast. In northern Woodward, three people were killed when the tornado struck a mobile home park.
The tornado exited Woodward about 12:23 a.m. and dissipated at 12:27 a.m.