70 million at risk from dangerous weather: Supercells gather over Plains threatening dangerous weather including tornadoes as hundreds rescued in Texas

Giant hail and strong winds with possible tornadoes threaten Plains as hundreds of people were rescued due to severe weather in Texas

Damaging severe thunderstorms are expected to gather over Oklahoma and Kansas, threatening dangerous weather across the region. Meanwhile, hundreds of people are rescued in areas of Texas that have been devastated by floodwaters.

The National Oceanic and Atmospheric Administration’s (NOAA) Storm Prediction Center has warned that parts of the central and southern Plains into the Midwest will possibly experience severe storms on Monday that could produce large hail, damaging winds and threats of tornadoes.

Western and central Oklahoma into central and eastern Kansas, including Oklahoma City and Wichita are of particular concern.

Strong and long-track tornadoes are possible and could stretch out into the night, also with the potential for severe and damaging wind gusts up to 80mph and giant hail, up to four inches in diameter.

The thunderstorms are expected to grow by late Monday afternoon into a group of supercells.

By Monday night, this strong weather may become a line of thunderstorms that will sweep eastward into the Midwest.

Texas Parks & Wildlife Department game wardens use a boat to rescue residents from floodwaters in Liberty County, Texas, on Saturday (AP)

At least 70 million people are at a “slight risk” or greater threat level for severe weather during the Monday to Wednesday period, Axios has reported the storm prediction centre forecasting.

Dangerous weather has already seriously affected neighbouring states after a third of Texas’ counties have announced disaster declarations after heavy rainfall inundated communities with floodwaters.

The body of a five-year-old boy was recovered from floodwaters near Fort Worth at 7.20am on Sunday while authorities were attempting to save people in a vehicle that was stuck in rapidly moving water.

Three occupants escaped from the vehicle that got stuck around 2am, but a 911 caller said they had been swept into the floodwaters while they were trying to reach safety.

A woman steps out of a mobile home in an unincorporated area in east Harris County near Houston on Saturday afternoon (AP)

While a man and a woman were rescued, the five-year-old boy was found deceased, the Johnson County emergency management coordinator said.

Fort Worth has experienced severe thunderstorms over the past few days, and the National Weather Service predicted that more isolated severe storms could be possible on Monday afternoon, with very large hail and damaging winds being the central threats.

Further south in the state, at least 400 people have been rescued from homes, vehicles and even rooftops in neighbourhoods around Houston, the Associated Press reported on Sunday, after days of rain left whole communities flooded with murky water and buildings ruined.

No deaths or serious injuries had been reported in that area, Harris County Judge Lina Hidalgo, the county government’s top executive, told CNN on Saturday night and added that 153 pets have also been rescued during the efforts.

Moving into Monday, conditions seem to be improving in areas, after the National Weather Service in Houston expired its flood watch after being in effect for 93 hours.

However, the service has warned that moderate to major river flooding will remain a concern for at least the next several days to over a week and is asking residents not to drive around any remaining barricades or enter into any flood waters.

Judge Hidalgo declared a disaster on Thursday in the county after heavy rainpour caused serious flooding in the area.

Mandatory evacuations were ordered in areas that were slammed with the worst conditions.

“What we’re going to see tonight and into the weekend will not be Hurricane Harvey, but we are going to see significant impacts,” Hidalgo said in a statement on Thursday.