Unseasonable weather in Chicago
The weather has been unseasonably warm in Chicago over the last few days with temperatures hitting 20C (68F) on Monday afternoon.
A record of 21C (70F) was set for November in 1918, while the average temperature for Chicago at this time of year is 7C (45F).
During Monday afternoon and evening, an active cold front passed from the west and interacted with the warm air, triggering a line of heavy rain, thunderstorms, strong winds and tornadoes.
A line of heavy rain and thunderstorms pass over Chicago during Monday evening
A tornado spanning 800 metres (half a mile) caused damage in the town of Caledonia, Illinois while hail up to 5cm (2 inches) wide fell in west and northwest Illinois.
Several children were injured after the tornado caused a bus to roll. Grain silos, barns and other buildings were also damaged.
Power lines were knocked down, cutting electricity to around nine thousand homes and affecting four thousand homes in Chicago.
Weather forecast for later this week
More severe weather is expected to hit the middle and lower Mississippi valley on Wednesday and into the early hours of Thursday (Thanksgiving Day).
Further severe thunderstorms, strong winds, large hail and perhaps tornadoes are expected.
By Thursday, colder air which follows on behind this weather system will plunge into the area. Temperatures in Chicago are expected to drop to the average of 6C (43F).
Forecasters are also warning that there will be a risk of snow - a stark contrast to the unseasonable warmth Chicago experienced on Monday.
