Firstly, it is always advisable to consider before you set off whether your journey is essential. If not, can it be delayed until after the rain has subsided? If so then plan your journey in advance, taking care to avoid areas which are prone to flooding, and factor in extra time to allow for slower speeds and potential congestion. It is also a good idea to let relatives and friends know your intended route and expected time of arrival and, where possible, travel with others.
How to drive in heavy rain.