Buick 2006 LaCrosse Owner's Manual page 268

The heavier the rain, the harder it is to see. Even if
your windshield wiper blades are in good shape, a heavy
rain can make it harder to see road signs and traffic
signals, pavement markings, the edge of the road, and
even people walking.
It is wise to keep your windshield wiping equipment
in good shape and keep your windshield washer
fluid reservoir filled with washer fluid. Replace your
windshield wiper inserts when they show signs of
streaking or missing areas on the windshield, or when
strips of rubber start to separate from the inserts.
CAUTION:
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Wet brakes can cause accidents. They will not
work as well in a quick stop and may cause
pulling to one side. You could lose control of
the vehicle.
After driving through a large puddle of water
or a car wash, apply your brake pedal lightly
until your brakes work normally.
4-18
Driving too fast through large water puddles or even
going through some car washes can cause problems,
too. The water may affect your brakes. Try to avoid
puddles. But if you cannot, try to slow down before
you hit them.
Hydroplaning
Hydroplaning is dangerous. So much water can build
up under your tires that they can actually ride on
the water. This can happen if the road is wet enough
and you are going fast enough. When your vehicle
is hydroplaning, it has little or no contact with the road.
Hydroplaning does not happen often. But it can if
your tires do not have much tread or if the pressure
in one or more is low. It can happen if a lot of water is
standing on the road. If you can see reflections from
trees, telephone poles, or other vehicles, and raindrops
dimple the water's surface, there could be hydroplaning.
Hydroplaning usually happens at higher speeds.
There just is not a hard and fast rule about hydroplaning.
The best advice is to slow down when it is raining.