Autumn downpours and aquaplaning: a new driver's first big water

September in Riga almost always opens with downpours. For an experienced driver that just means a wet road. For a new driver it is the first meeting with something the course only mentioned in passing: the car is going straight, and suddenly the steering goes light and empty, as if the wheels have stopped holding anything. That is aquaplaning. What frightens people is the suddenness — so let's take it apart in advance, on dry ground.

What happens under the tyre

One of the tread's main jobs is to channel water out of the contact patch. As long as it keeps up, the tyre grips the asphalt. When there is too much water and too little time, a wedge of water builds under the wheel: the tyre lifts and slides on a film of water without touching the road. In that moment the car responds neither to the steering nor to the brakes.

The risk is built from four factors, and they all work together:

• speed — the faster you go, the less time there is to disperse water;
• water depth — a puddle, a rut, a stream along the kerb;
• tread wear — a worn tyre clears water far worse than a new one;
• tyre pressure — an under-inflated tyre loses its contact patch sooner.

There is no exact "aquaplaning speed": on worn tyres and in a deep rut a car can start floating where nothing would happen on fresh tyres.

Where it happens on Latvian roads

Most often not in a courtyard puddle, but at speed:

• Ruts. On busy trunk roads, heavy traffic wears longitudinal grooves into the asphalt. In rain these are ready-made water channels. If the car starts floating in a rut, shift half a car's width left or right, onto the crest between the ruts.
• The edge of the right lane. Water drains towards the kerb, and it is deeper there than it looks.
• Dips and stretches where water does not drain. After a long downpour the asphalt can sit under a continuous sheet of water.
• The first minutes of heavy rain — the water is still mixed with dust and rubber particles, and the road is at its slipperiest.

How it feels and what to do

There is one very characteristic sign: the steering suddenly goes light, the revs may jump, and the car stops answering steering inputs. From there, three rules — all of them about avoiding sudden moves:

1. Lift off the accelerator. Do not brake. The car will slow by itself and the tyres will regain contact.
2. Keep the wheel straight. If you turn the wheels while sliding, the car will be thrown sideways the moment grip returns.
3. Brake only if a collision is unavoidable — and even then, gently.

Once grip is back — usually a matter of seconds — calmly reduce speed and carry on slower. On a wet road it is better to switch cruise control off in advance: it will hold a speed exactly where you should be shedding it.

Prevention: tyres and speed

The law in Latvia requires at least 1.6 mm of tread on summer tyres for cars and light vehicles (up to 3,500 kg). But the legal minimum and the safe minimum are different things: specialists advise replacing summer tyres already at around 3 mm, because below that mark the ability to clear water drops off sharply. From 1 December to 1 March winter tyres with at least 4 mm of tread are mandatory — more on that in the winter driving guide. Facts verified in July 2026 — check current requirements on csdd.lv and likumi.lv.

The road traffic rules are on the side of the cautious here: speed must suit road and weather conditions (Rule 99), on hazard you must slow down, up to a full stop (Rule 100), and your following distance must let you avoid a collision (Rule 105). In rain that means one simple thing: the permitted 90 km/h outside town is a ceiling for ideal conditions, not a norm for a downpour. Rural speed and overtaking get their own article.

Visibility: the other half of the problem

Heavy rain takes away not only grip but also your view:

• Wipers and washer must work flawlessly — in autumn this is not a detail, it is basic equipment.
• Lights. Daytime running lights or dipped beam by day; dipped beam in the dark and in poor visibility (Rules 160–161). In a downpour your headlights are less for you than for the people who need to spot you.
• Fogged-up windows. Blower onto the windscreen; the air conditioner dries the air fastest. A rag on the glass while moving is a bad plan.

If your exam is coming up

Autumn candidates take their test in the rain — the Road Traffic Safety Directorate (CSDD) does not cancel exams because of precipitation, and checking the wipers before moving off is part of preparing the vehicle. The examiner is not looking for bravery but for a speed that matches the conditions: slightly under the limit in a downpour is fine; crawling and obstructing the flow is an error. How the autumn exam works as a whole is covered in a separate article.

Your first big water is a skill best learned with an instructor beside you, not alone on a trunk road. One rainy lesson in autumn, and "the car is floating" turns from a horror story into a clear situation with clear actions. You can book a lesson online.