See also:

Wet roads
WARNING After driving in heavy rain for some time without applying the brakes or through water deep enough to wet brake components, the first braking action may be somewhat reduced. You have ...

The windshield wipers are inoperative
The windshield wiper drive is malfunctioning. Select another wiper speed on the combination switch. Have the windshield wipers checked at a qualified specialist workshop. ...

Parking brake
If you drive on wet roads or dirt-covered surfaces, road salt and/or dirt could get into the parking brake. In order to prevent corrosion and a reduction in the braking power of the parking brake ...