In the United States, a flash flood watch is issued by the National Weather Service (NWS) when weather conditions are favorable for very heavy rain that could cause flooding or flash flooding. A watch does not mean that flooding is actually occurring, only that weather conditions have created or will create a significant risk for it. If flooding actually does occur, a flood warning or flash flood warning would be issued and immediate action should be taken. A flood warning or flash flood warning is issued when flooding is imminent or already occurring. When flood warnings are issued, it means that area waterways will likely soon be in flood. Not all flood watches suggest that large-scale flooding, such as during landfallingtropical cyclones, is possible.