Originally Posted by Roelof

If that will help.....

It is not the splashing water filling up an air filter. Water is in the air, when sucked through the filter water will stay behind if you did not use the right oil. A good oiled filter with the right oil will not hold water and will not block the airflow. But the water can go through the filter.
Some people are using diesel filters which seems to filter out water.

In the rain I do not use an air filter. I modified an INSBOX with some tubes so air has a free flow but dirt and water can not reach the carburator. With rain there is not much dust and other small particles in the air.....