Woodward, Oklahoma (CNN) -- The death toll from a weekend tornado in Woodward, Oklahoma rose to six Monday with the death of a critically injured man in the hospital, a city official said.
The man, whose name has not been released, died at a hospital in Amarillo, Texas, about 160 miles away, Woodward emergency manager Matt Lehenbauer said.
His wife remains hospitalized in critical condition, Lehenbauer said.
The storm struck after midnight Sunday, taking aim at the Hidden Valley Mobile Home Park in Woodward, killing Frank Hobbie and his two young daughters, ages 5 and 7.
Two other victims, Derrin Juul and a 10-year-old girl presumed to be Juul's daughter, died when powerful winds rolled their car several times, Woodward Mayor Roscoe Hill said.
The Woodward storm was one of dozens of tornadoes believed to have been spawned by a furious storm system that wreaked havoc across large swaths of 10 states in the Midwest and Plains over the weekend.
The only known casualties occurred in the northern Oklahoma city of about 12,000, about 85 miles west of Enid. At least 29 people were injured, officials said.
By early Monday, the National Weather Service lifted the last of widespread tornado watches in Minnesota, Wisconsin, Arkansas, Iowa and Illinois after threats of another furious outbreak of tornadoes never materialized. Strong thunderstorms remained a possibility during the early morning hours, the service said.
The weather service's Storm Prediction Center received 10 reports of tornadoes Sunday -- the last a reported touchdown in McLeod County in Minnesota -- and 122 reports of tornadoes Saturday.
Officials credited working early warning systems elsewhere in the region with preventing more fatalities.
Advisories from the system were issued two days in advance, rather than just hours, and were "remarkably accurate," said Kansas Gov. Sam Brownback. "People took it very seriously."
But in Woodward, Oklahoma, where 89 homes and 13 businesses were destroyed, the storm took out the transmitter for the tornado warning siren system. "We lost our manual override" when the electricity was knocked out, City Manager Alan Riffel said.
Given that and timing of the tornado -- after midnight, and after other severe weather had barreled through -- Oklahoma Gov. Mary Fallin said, the human cost could have been even worse.
"It's remarkable that we didn't have more loss of life in Woodward," she said late Sunday afternoon.
Fallin has declared a state of disaster emergency in 12 counties in order to help expedite resources.
In southwest Iowa, residents of Thurman were digging through debris after a tornado struck Saturday.
"About 75% of the homes are damaged or destroyed," said Mike Crecelius, Fremont County's emergency management director.
Four truckers whose rigs were blown off Interstate 29, by the same tornado that struck Thurman, were the only ones hospitalized with storm-related injuries, the weather service said. The agency reported the twister had winds between 111 and 135 mph as it caused a half-mile-long damage path over 10 miles.
Earlier, a confirmed tornado struck a hospital in Creston, Iowa, blowing out windows and damaging the roof, said John Benson of the Iowa Homeland Security and Emergency Management agency. There were no major injuries reported, and patients were relocated to other area hospitals.
One of the biggest cities hit over the weekend was Wichita, Kansas, where resident Katie Sykes said torrential rains produced a "river in my front yard" and the prospect of a tornado had her shuddering in fear.
"When I was little, we prepared for storms, hearing the sirens and then going to the basement. And going through this experience, I felt like a little kid, young and scared," Sykes said.
A tornado churned across the southern part of the city, home to a number of aircraft-related manufacturers. The tornado struck Boeing and Sprit AeroSystems, officials said.
A few hundred employees were working at a Spirit Aero Systems plant, producing fuselages and other equipment for Boeing aircraft, said company spokesman Ken Evans, when a twister came through and caused the roof to collapse. No one was injured, and workers have been told not to come in until Wednesday as the damage is assessed.
CNN's Rob Marciano reported from Oklahoma and Maria P. White from Atlanta.