If you are unable to see the road ahead while driving through heavy rain or fog, and your wipers do not , you should:

If you are unable to see the road ahead while driving through heavy rain or fog, and your wipers do not help, you should pull off the road completely until visibility improves.
This is the wisest thing to do in such conditions, if you want to avoid having a car accident. If you cannot see ahead of your car when it is raining or foggy, you should avoid driving, because you may injure yourself or somebody else.