Rain fog and hydroplaning — Minnesota Permit Test

Rain fog and hydroplaning on the Minnesota permit test — 6 rules, each with the reason behind it and a question on it while it is fresh.

The rules

In heavy rain or fog, reduce speed, increase your following distance and be ready to stop.

You can see less and stop less well at the same time, so both the speed and the gap have to change.

If you encounter thunderstorms or fog, reduce speed, use extra caution and be prepared to stop. Increase your following distance.

Minnesota Driver’s Manual, p.81

Headlights must be on when you cannot see more than 500 feet ahead and when it is raining, snowing, sleeting or hailing, and they should be on low beam.

High beams bounce off falling water and fog straight back into your own eyes.

Keep them on low beam to reduce glare.

Minnesota Driver’s Manual, p.81

If you cannot see a safe distance ahead, pull off the road and stop until visibility improves.

A car stopped off the road is a nuisance. A car driving blind is a crash waiting for somebody.

If you cannot see a safe distance ahead, pull off the road and stop until visibility improves.

Minnesota Driver’s Manual, p.81

At 35 mph or less most tires wipe water off the road, but at higher speeds water can lift them off the surface.

That lift is hydroplaning, and once it starts the steering and brakes do nothing at all.

At speeds of 35 mph or less, most tires will “wipe” water off the road surface to keep tires in contact with the road.

Minnesota Driver’s Manual, p.82

When tires hydroplane they lose all contact with the road, so you cannot brake, accelerate or change direction.

The car keeps going the way it was pointed, and nothing you do with the controls changes that.

If your tires begin to hydroplane, take your foot off the gas pedal.

Minnesota Driver’s Manual, p.82

Hydroplaning can happen at any speed if the water is deeper than the tread of your tires.

The tread has to move the water out of the way, and it can only move so much.

However, hydroplaning can occur at any speed if the depth of the water on the road is greater than the depth of the tire treads.

Minnesota Driver’s Manual, p.82

On the test

What does the manual say to do in thunderstorms or fog?

Reduce speed and increase following distance. You can see less and stop less well at the same time, so both the speed and the gap have to change. Minnesota Driver’s Manual, p.81: “If you encounter thunderstorms or fog, reduce speed, use extra caution and be prepared to stop. Increase your following distance.”

How this works

Most practice tests hand you a bank of questions and leave the manual somewhere else. This one puts them together.

You read one law and the reason behind it, then answer a question on that law while it is still fresh. Get it right and you move on; get it wrong and you have found the gap while it is cheap to fix, not on the morning of the exam.

Learning one rule at a time, and proving it immediately, is what turns a manual you skimmed into something you actually know — and it makes studying feel like getting somewhere rather than like waiting to find out.

What it costs

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Where these come from

Every rule here is checked against Minnesota Driver’s Manual, published by the Minnesota Department of Public Safety, and against the state code itself. Last checked 2026-09-22.