Rain is the bad weather most drivers face most often.
Because it is so common, it is easy to forget how much it changes the way a car behaves.
Wet pavement lengthens your stopping distance, hides the lane lines and can lift your tires right off the road.
This guide explains why rain is tricky, how hydroplaning happens and what to do if your car starts to slide.
Why the first rain is the most slippery
Many drivers assume the road is most dangerous in a downpour.
In fact, the start of a rainstorm can be even worse.
The California Driver Handbook warns that pavement can be very slippery when it starts to rain.
This is especially true after a long dry, hot spell.
Oil and dust build up on the road surface, and a light rain mixes them into a slick film.
Heavier rain eventually washes much of that away, but the first minutes catch many drivers off guard.
The handbook advises slowing down at the first sign of rain, drizzle or snow on the road.
Slow down and add space
The simplest rule for wet roads is to drive more slowly than you would on a dry road.
The California handbook gives a specific target.
On a wet road, reduce your speed by 5 to 10 mph.
That is a minimum, not a goal, and heavy rain may call for much more.
Leave extra space between your car and the vehicle ahead, too.
A wet road needs more distance to stop, and spray from other cars can hide brake lights.
When you cannot see far ahead
In a heavy rainstorm, visibility can drop fast.
The handbook notes you may not see more than 100 feet in front of your vehicle.
When you cannot see farther than 100 feet, it says it is not safe to drive faster than 30 mph.
If even that feels too fast, it is time to find a safe place to stop.
Make sure you can see and be seen
The California handbook lists three things to turn on in heavy rain:
- Windshield wipers, set fast enough to keep the glass clear.
- Low-beam headlights, so other drivers can see you and your taillights are on.
- The defroster, to keep the inside of the windshield from fogging up.
The handbook also says not to drive using only your parking lights.
Worn wiper blades smear water instead of clearing it.
Replace them before the rainy season if they streak, chatter or skip.
What hydroplaning is
Your tires need contact with the pavement to steer, brake and accelerate.
Tire treads are designed to channel water out from under the tire.
When there is more water than the treads can move, the tire can ride up on a thin layer of water.
The California handbook describes hydroplaning as a vehicle riding on water because the tires lose all contact with the road.
In that moment, a slight turn, a touch of the brakes or a gust of wind can throw the car into a skid.
Speed, worn tires, low tire pressure and deep standing water all make hydroplaning more likely.
How to avoid hydroplaning
The handbook gives four simple ways to prevent it:
- Drive slowly.
- Steer around standing water, if possible.
- Slow down if you hear sloshing sounds from the tires.
- Slow down when changing lanes or direction.
A few other habits help as well.
- Drive in the tire tracks of the car ahead, where some water has already been pushed aside.
- Avoid the outer lanes on roads where water collects near the edges.
- Keep your tires properly inflated and replace them when the tread is worn.
- Turn off cruise control on wet roads so you stay in full control of the throttle.
What to do if your car starts to hydroplane
You may feel the steering go light, or the engine may rev without the car speeding up.
The natural reaction is to slam on the brakes, but that is the wrong move.
The California handbook is clear about what to do:
- Stay calm and keep a firm grip on the steering wheel.
- Slow down gradually by easing your foot off the accelerator.
- Do not use the brakes, because sudden braking may cause you to lose control.
- Keep the steering wheel pointed where you want to go, without sharp turns.
- Wait for the tires to regain grip, which you will feel as the steering firms up.
If the car starts to skid
Sometimes a wet road leads to a full skid.
For a skid on a slippery surface, the handbook gives these steps:
- Slowly remove your foot from the accelerator.
- Do not use the brakes.
- Turn the steering wheel in the direction of the skid.
- Try to get a wheel onto dry pavement.
Steering in the direction of the skid means turning toward where the rear of the car is sliding.
Make small, smooth corrections rather than large swings of the wheel.
Wet brakes after deep water
Driving through deep puddles can soak your brakes and make them weak for a short time.
The California handbook suggests a way to dry them.
Lightly press the accelerator and brake pedals at the same time, but only until the brakes dry.
Do this at low speed, with no traffic close behind you.
Never drive into flooded roads
Heavy rain can quickly turn a dip in the road into a flood.
The National Weather Service warns that it takes just 12 inches of rushing water to carry away most cars.
Just 2 feet of rushing water can carry away SUVs and trucks.
The NWS also notes that the road itself may have collapsed under the water.
Never drive around barriers that block a flooded road.
Turn around and find another route, even if it adds time to your trip.
When to pull over
Some storms are simply too intense to drive through safely.
If you cannot see the road edges or the car ahead, slow down and look for a safe place to stop.
A parking lot or rest area is far better than the shoulder of a busy highway.
If you must stop on the shoulder, pull as far off the road as you can and turn on your hazard lights.
Wait until the heaviest rain passes before you continue.
Common rain driving mistakes
- Driving at the posted speed limit on a wet road.
- Following too closely in heavy spray.
- Relying on parking lights or automatic lights that leave the taillights off.
- Using cruise control in the rain.
- Braking hard when the car starts to hydroplane.
- Driving through water of unknown depth.
The bottom line
Rain asks you to drive more slowly, leave more room and keep your inputs gentle.
Watch out for the slick first minutes of a storm and for standing water that can cause hydroplaning.
If the car slides, ease off the gas, avoid the brakes and steer smoothly.
When the rain is too heavy to see, or water covers the road, the safest choice is to stop or turn around.
Sources and Further Reading
- California DMV: California Driver Handbook, Section 8, Safe Driving — supports the advice on slippery first rain, reducing speed by 5 to 10 mph on wet roads, the 100 feet and 30 mph visibility rule, wipers, low beams and defroster, hydroplaning prevention and recovery, skid steps and drying wet brakes.
- National Weather Service: Turn Around Don't Drown — supports how little rushing water can carry away cars, SUVs and trucks, and the warning never to drive around barriers on flooded roads.