India, Aug. 11 -- St Louis in Missouri is in for severe thunderstorms this afternoon or evening, the National Weather Service has announced.

This comes as they predicted slight risk of excessive rainfall in the Upper Midwest to the southern Plains plains area, while maintaining a moderate risk of excessive rainfall across parts of Kansas, Missouri and northern Oklahoma through Monday morning.

A slow-moving, nearly stationary frontal boundary is the cause for the downpour, and will bring more showers and thunderstorms in the next couple of days, the NWS said.

Yesterday, Milwaukee saw flash floods, and the Wisconsin State Fair was forced to close early.

While skies are expected to clear by Tuesday, here's what you need to know about St ...