Showers and thunderstorms that continued moving through the Chicago area Monday afternoon prompted a flood warning and caused the cancellation of hundreds of flights at O’Hare International Airport.

Torrential downpours, small hail, frequent lightning and winds up to 60 mph are expected to pummel the area until about 11 p.m., according to the National Weather Service. As a result, a flood warning will remain in effect until 5:15 p.m. for Chicago and many of the surrounding suburbs.

The powerful storms led to 344 flight cancellations at O’Hare, as well as delays of more than an hour, according to the Chicago Department of Aviation. Midway International Airport has canceled a single flight, with travelers experiencing 16-minute delays.

People affected by the storm should head inside for shelter and avoid crossing roads that have flooded, the weather service said. Localized flooding is still possible in areas that haven’t been inundated with rain.

On Tuesday, mostly sunny conditions and temperatures in the high 80s are expected for much of the day, the weather service said. A small chance of additional thunderstorms is also in the forecast.