Flash floods occur when rain is falling so fast that storm drains can't keep up and water starts to overflow and from there, it can continue to accumulate and get into buildings.
What to do when you see flooded roadways:
Do NOT drive into the water, the water can easily appear more shallow than it actually is. That's what gets a lot of people killed as well...people driving into flooded roads and getting swept off the road.
Make sure you move to higher ground. Avoid areas that are prone to flooding. If you must drive during heavy rains that are causing flooding at night, be sure to take extra care when driving.
That's all for flash flooding, tomorrow's topic will be covering Lightning safety.