"More tornados are on the way today, most likely late this afternoon into the evening", Rich Otto, a forecaster for the National Weather Service said, adding the warnings stretched from Texas, Oklahoma and Kansas eastwards to Arkansas and southwest Missouri.
The service said: "The risk will be particularly high across central and north central Oklahoma where some areas will receive more than 5 inches of rainfall".
The National Weather Service's Tulsa Office said the confirmed tornado was reported around 6:37 a.m. over the airport and moving northeast at 50 miles per hour. Flood potential is high, especially across areas where the ground remains saturated from recent rains and flooding. Earlier, two tornadoes formed simultaneously near the town of Crescent, Oklahoma.
More tornadoes, along with hail and damaging winds were predicted as the storms moved to the east.
In the past three days, 52 tornadoes were reported across seven states, CNN Meteorologist Michael Guy said.
After the sun set, the severe weather continued as heavy rain and flooding wreaked havoc on some roads.
"More isolated but still potentially unsafe severe weather, including tornadoes and destructive winds and hail, is possible in surrounding parts of Texas, Oklahoma, Kansas, and Arkansas".More news: Mobile details confirmed ahead of summer beta
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Forecasters warned that more than 2 million people lie in the path of a series of storms that could produce an outbreak of violent, large-scale tornadoes across parts of Texas and Oklahoma, along with baseball-size hail, flash flooding and hurricane-force winds.
"On top of emergency crews trying to fix power lines and other damage from the tornado", the department said, "the roads are now flooding due to the intense rain".
- A tornado watch for southwestern Missouri, eastern Oklahoma and western and central Arkansas is in effect until 8am CDT (2pm BST).
"We're seeing reports of flooding and water rescues across (northeast) Oklahoma", state emergency management spokeswoman Keli Cain told CNN. The levee near Jefferson City's airport holds back water up to 30 feet (9.14 meters), Cole County Emergency Manager Bill Farr said, but the National Weather Service expects a crest of 32.3 feet (9.85 meters) Thursday.
The Monday storms followed a spate of tornadoes in the Southern Plains on Friday and Saturday, leaving widespread damage and some people injured.
Severe thunderstorms will drench and flood parts of Oklahoma Tuesday, following on the heels of a series of tornadoes that touched down in that state and others.
While many may have been able to get to shelters, local and national weather stations stressed to Oklahoma City residents idents that OKC does not have public tornado shelters.