During high winds and flash floods the best idea is to stay in your home. Trying to take on a storm in traffic will only make it worse for everyone on the road. If you are out on the roads this is the best way to navigate your way through.
Many modern cars will make it through some bad floods but if can you should try to go around, but If there is no other way around then try to find the lowest point of standing water. 4-6 inches is the most you should go through of moving water. If there is vehicles in front of you be sure to cars similar to that of your own. If you see them struggle find a different way. If not then be sure to follow them keeping the power low and staying within the first gear.
Why only first gear? Keeping the revs high can keep the water from entering the exhaust pipe and not applying too much power at the start can create a bow wave at the front of the vehicle that will create a depression in the engine bay alloying clean air through with no water. Beamed 4×4 vehicles should not try this technique.
Just like driving in the rain staying within the speed limit and driving carefully is the best way to go. Travelling at high speeds can cause aquaplaning, this is were the tyres are no longer gripping on the road due to a layer of water that has built up in between the surface and the road. This causes total loss of control and prevents the car responding to your movements on the steering wheel. Be sure to check the cars coming the other way, as other drivers may not be as careful! There are plenty of bad drivers on the road that no matter how bad the storm or weather they will still drive as fast as they can to get to their destination. Especially if they are coming the other way through a flood at the same time you are. Oncoming vehicles can create bow waves that will then disrupt your bow wave you are trying to create, soaking the engine bay and even putting the exhaust under pressure.
In the worse case scenario that your car stops working climb out of your vehicle leaving the bonnet closed to stop water from accessing it even more. Wade out to dry land and wait for a recovery. You can always try to re start your car the once or twice. Re starting your car to many times can flood the engine bay with water. Figures show that 54% of us on the roads endanger themselves and their own vehicles by driving through deep moving floodwater. The research that saw 21,165 take part of a survey also said that 27% of car owners would drive through moving flood water that is deeper then 30cm. The Environment Agency and the AA have strongly advised for many years not to try driving through any floodwater deeper than 10cm.
Source: Wheelwright Blog