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From tire tread to floodwater: 9 tips for driving in heavy rain

Nine tips for driving in heavy rain and flooding, from reading flood warnings and checking tires to recovering from hydroplaning and knowing when to turn around

Rain takes away two things a driver depends on at the same time: traction and visibility. A film of water between rubber and asphalt reduces grip. Spray, glare and fogged glass shrink the view ahead. Floodwater adds a third problem. Its depth and current are hard to judge from behind the wheel, and the road beneath it may be washed out.

That combination makes driving in heavy rain a different task from ordinary driving, not just a slower version of it. Stopping takes longer. Abrupt steering or braking that a car would absorb on dry pavement can start a skid. A dip that looks like a puddle can hold enough water to stall an engine or move the car. Choices that seem minor in good weather carry more weight. Two examples are how closely to follow a truck and whether to take a familiar underpass.

The tips below are a selection of practical steps, not a complete rulebook. They follow the order in which a driver tends to face them. The first covers the decision made before leaving home. That means reading weather alerts and knowing what the National Weather Service means by a flood watch versus a flood warning. The next tip deals with the car itself: tire tread depth, tire pressure and wiper blades. Those three items set how much margin a vehicle has on wet pavement.

From there, the list moves to technique on the road. That includes speed and following distance, headlight use, recovering from hydroplaning, clearing a fogged windshield and handling spray from trucks and buses. Each of these deals with grip or visibility.

The final tips address floodwater directly. They explain why official guidance tells drivers to turn around rather than cross a flooded road. They also cover what to do if a car stalls in rising water. The last one covers what to check once a vehicle is past standing water, from the brakes to the roadside hazards a storm leaves behind.

Each tip stands on its own. A reader can go straight to the situation at hand, whether that is a storm in the forecast, a skid on the highway or water across the road ahead.

Flood watch vs. flood warning

Check the National Weather Service forecast and active alerts before leaving, then decide whether the trip needs to happen at all. Knowing a flood watch from a flood warning tells a driver how serious the threat is.

The wording of those alerts matters. The National Weather Service issues a flood watch when conditions could produce flooding. A watch means the ingredients are in place, but water has not yet started covering roads. It is a signal to prepare and to keep checking for updates.

A flood warning is a step up. The National Weather Service issues one when flooding is happening or about to happen in the area named. For a driver, that changes the question from whether to be ready to whether to be on the road at all. Postponing the trip is the simplest response.

A flash flood warning carries the most urgency of the three. It means a flash flood is occurring or imminent. Flash flooding is a rapid rise in water that can develop within minutes or hours of intense rain. Small streams, dry creek beds and city streets with overwhelmed storm drains can fill quickly. In the U.S., flash flood warnings can be pushed to mobile phones through the Wireless Emergency Alerts system. A driver who receives one mid-drive should pull over somewhere safe before reading it. NOAA Weather Radio also broadcasts National Weather Service alerts around the clock.

If the trip goes ahead, the route deserves as much thought as the departure time. Water collects first in the lowest places. Underpasses, dips in the road and streets that run beside creeks or rivers are the spots most likely to flood. Choosing roads on higher ground cuts the chance of meeting standing water, even if the drive takes longer. Knowing a second route helps in case the first one closes.

Two simple preparations round out the plan. Leave with a fully charged phone. It keeps maps, alerts and emergency calls available if conditions change. Leave with enough fuel, too. Detours around closed roads add miles, and traffic can back up for long stretches during a storm.

Tire tread depth and wiper blades

Tire tread and wiper blades decide how well a car holds wet pavement and how clearly its driver sees in a downpour. Check both before the wet season begins.

Tread has a specific job on wet pavement. The grooves cut into a tire channel water out from under it. That keeps the rubber in contact with the road. As the tread wears, those grooves get shallower and move less water. Worn tires lose grip on wet pavement much sooner than tires with deeper tread.

The legal minimum tread depth in most of the U.S. is 2/32 of an inch. In the U.K., the limit is 1.6 millimeters. The U.K. rule applies across the central three-quarters of the tread and around its full circumference. That minimum marks the point at which a tire must be replaced, not the point at which wet grip begins to fall........

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