When the rain is falling or snow is melting, a driver typically doesn't have to worry about water getting into their vehicle. As long as the windows are closed, the cabin should remain dry even during a downpour.

This protection from the element doesn't occur because the vehicle is completely sealed off from the elements. In several more exposed areas, drain holes provide a place for water to exit. If the drain holes become blocked, your vehicle is more at risk of water damage and rusting.

The most common location for drain holes is at the bottom of the doors. Since rainwater can seep in past the door seal, the drain holes ensure that water will not collect under the seal and go unnoticed.

Vehicles often incorporate drain holes in other areas as well. Rick Popely, writing for the automotive site Cars.com, says many vehicles will have drain panels in the rocker panels and rear quarter panels, both of which are located near the doors. Vehicles may also have drain holes beneath the windshield and near the trunk to keep water from collecting in these areas.

Over time, dirt and debris can plug up the drain holes. Popular Mechanics says they may also be inadvertently blocked during a vehicle repair.

If water cannot run out of the vehicle, it will instead take a different channel. This can cause water to make its way into the interior of the vehicle, causing stains and deterioration. Water can also pool in one area and cause metal to rust.

The likelihood that you'll experience a problem with the drain holes depends on your vehicle design and the place you tend to store and drive your vehicle. Popely says some vehicles will be more susceptible to drainage problems because the drain holes are too small or too infrequently spaced. Areas with lots of dust, mud, falling leaves, and other debris will increase the chances that foreign objects will get washed into the drain holes and block them.

You can test how well the drain holes are working by running a hose over the certain parts of the vehicle. When you spray the windshield, trunk, and doors, you can check to see if the water is draining properly. If it is collecting or draining slowly, you likely have a blockage.

The high pressure sprays of a car wash, or even a regular garden hose, may be enough to blast the debris out of the drain holes. But they can easily fill up again if the design or environment is contributing to the problem.

When you take a vehicle in for a car wash or detailing job, an inspection of the drain holes is usually not included. However, you can ask a professional to include this service as part of their work.

The windshield drain holes are the easiest ones to access. Kurt Schleier, writing for the United Kingdom mobile servicing network ClickMechanic, recommends removing leaves and other debris from the cowl as often as you can. Clearing the space around the trunk seal is also a task you should do whenever possible.

The drain holes on the doors, rocker panels, and rear quarter panels will require you to peer underneath the vehicle. You should be able to locate the openings and see if they are blocked.

Clearing out the drain holes can be done using a screwdriver, bent coat hanger, or similar tool. Pat Goss, writing for the automotive TV series MotorWeek, says you can wrap the end of the tool in tape to ensure that the sharp point won't cause any damage.

You should also avoid lying directly underneath the drain holes when doing this work. If you do so, you're almost certain to get a face full of debris and stagnant water.