Is it actually dangerous to use cruise control in the rain?

With heavy rain currently bearing down across the east coast of Australia, those who have a freeway commute home from work may be tempted to select cruise control for a bit of comfort for their right foot.

Those who have been taught professionally might have been told that using cruise control in the rain may not be the best idea.

As explored by a plethora of questions asked on Reddit, users have argued whether using cruise control in the rain could cause an accident.

The main argument is that there is a heightened chance of aquaplaning, which could lead to an accident. Even big brands such as Toyota warn in the manual not to use cruise control in the rain.

“Do not use dynamic radar cruise control with full-speed range in any of the following situations, [including] on slippery roads, such as those covered with rain, ice or snow,” as per the 2024 Toyota RAV4 owners manual.

But with that being said, do you have a heightened chance of crashing or aquaplaning while having cruise control activated in the rain?

To understand if it is dangerous to use cruise control in the rain, you must first understand what aquaplaning is.

Aquaplaning occurs when water builds up on the road, causing the tyre to lose contact with the road and skip across the water like a stone. The pooled water acts as a barrier, preventing your tyres from making contact with the road.

Think of it as one moment you are travelling along with full control, and the next, you are essentially a passenger in a hovercraft drifting along until your tyres can make contact with the road again.

No amount of braking or steering input will work. The best way to describe it is that the car will feel completely weightless.

You can also experience a partial hydroplane when only part of the tyre is subjected to this phenomenon; you will feel the steering become light and the car will lose some control.

To understand more about aquaplaning, you can read our previous story here.

The idea that using cruise control in the rain causes aquaplaning is a myth. However, the idea that it makes you more susceptible to it may not be.

We spoke to Dicky Tong, an accredited driving instructor, who said that using cruise control in the rain isn’t recommended, but it won’t cause the car to aquaplane automatically.

“Cruise control should not be used in slippery conditions such as rain, ice, or snow, where losing control is a real risk," said Tong.

"Although modern vehicles have safety systems that can cut power or apply brakes when they detect a loss of grip.”

Most modern-day cruise-control systems will switch off in any event where traction control cuts in. The traction-control system works via speed sensors on the wheels, and in layman's terms, it will cut power to the wheels when wheel speed is increased on one or more wheels compared to the others.

Now, there are more intelligent systems, but this is the crux of how a traction-control system works. When you hit a patch of standing water that causes the car to aquaplane, the lack of resistance on the affected wheels will cause them to rotate faster than those that maintain grip on the road, thus causing traction control to cut in and the cruise control to be switched off, all within a matter of milliseconds.

This is the case for most cars from the 2000s onwards. However, some older vehicles may either not have traction control, less intelligent systems, or a manual cruise-control system.

Modern vehicles use an electronic throttle body that works in tandem with the electronic control unit to run all operations inside the vehicle. Aftermarket cruise control, or older vehicles without an electronic throttle body, have a cruise-control system that quite literally works by holding the throttle open with a physical cable.

While these will still switch off when you hit the brakes, you might not be so lucky in the event of aquaplaning. Without traction-control intervention, the cruise control could hold the throttle open even when there is a loss of traction – causing a continued acceleration while out of control.

Tong also mentioned that, quite possibly, the most important reason cruise control shouldn’t be used in the rain is complacency.

“Relying on cruise control can make drivers less attentive. Cruise control holds the throttle until those systems step in, which can delay your response and lengthen stopping distances. By not using cruise control in the wet, you stay more alert and ready to react to changing road conditions. That’s why most car manufacturers specifically warn against using cruise control in slippery conditions,” said Tong.

Having full control over the car in adverse weather conditions means you remain alert and aware of any standing water on the road.

Kevin Flynn, Master Instructor at Driver Dynamics, had a similar point of view to Tong. You need to vary your driver inputs in the rain.

"It's not advisable simply because you need to vary your driver inputs according to changing conditions – for example, if you are confronted by an increase in rain, or see a large gathering of water on the road, drivers will normally ease off the accelerator and reduce speed – whereas cruise control will keep the speed that it is set at," said Flynn.

"If it's very light rain and the road is only slightly wet, it can be fine to use cruise. However, if you are driving in any sort of decent rainfall, I would advise against it."

Jumping hard on the brakes while aquaplaning is one of the worst things you can do; it could upset the balance of the car and send you into a spin. If you’re just letting cruise control run its course, feeling a loss of traction might lead you to jump straight on the brakes.

"The best advice is primarily to reduce speed, ease off the accelerator and allow the car to slow down. I must say that modern tyres with a sensible amount of tread are incredibly good at not aquaplaning – far better than tyres from as little as 15–20 years ago," said Kevin Flynn from Driving Dynamics.

By keeping the wheel straight, you will be able to pass over the puddle into a clear area where your car can regain traction. If the car begins to skid sideways, you should begin to steer in the direction you want to go and brace for the vehicle to regain traction.

To read more about aquaplaning, and how you can prevent it, head here. The crux of it is that it's best to leave the cruise control alone in the rain. Regardless of the age of your car, remain attentive and fully in control of the vehicle while in adverse conditions.

Zane Dobie comes from a background of motorcycle journalism, working for notable titles such as Australian Motorcycle News Magazine, Just Bikes and BikeReview. Despite his fresh age, Zane brings a lifetime of racing and hands-on experience. His passion now resides on four wheels as an avid car collector, restorer, drift car pilot and weekend go-kart racer.

Read more about Zane Dobie