Fall's first cold morning can trigger a chain reaction before you even leave the driveway: Frost coats the windshield, the tire pressure lights up on your dash and fog hides the road ahead.

The weather setup starts overnight

Fall's longer nights give the ground more time to release the heat it absorbed during the day. Clear skies let that heat escape more efficiently, while light winds keep warmer air above from mixing back down to the surface. High pressure often sets up these exact conditions — clear and calm.

(MORE: Weather alerts decoded: What advisories, watches and warnings really mean)

Weather in your inbox

Forecast Location

Sign Up

By signing up you agree to the Terms & Privacy Policy. Unsubscribe at any time.

This process is known as radiational cooling, and it steadily lowers the temperature of the ground and the air just above it.

Once air reaches the dew point, water vapor condenses into the dew you see on grass or cars — but exposed surfaces like windshields and rooftops can drop below freezing even when the air itself is still a little bit above 32 degrees, causing frost to form instead.

Metal and glass radiate heat especially efficiently, and cars and rooftops are more exposed to open sky, so they cool to the frost point faster than the ground around them. That's why your windshield can be frosted over while the grass a few feet away is still just damp with dew.

Get More of Our News on Google

Set The Weather Company as a 'Preferred Source' to get quicker access to the news you value.

Visibility can collapse quickly

Cold air is heavier than warm air, so it sinks and pools in valleys and other low spots. Those pockets can reach the dew point before the surrounding hills do, which is why fog often forms there first.

Rivers, lakes, wetlands and damp fields add extra moisture to the air, making nearby roads — especially rural, agricultural ones — even more prone to fog.

Drivers can hit a fog bank with almost no warning, watching visibility drop from several miles to just a few hundred feet in seconds. And it doesn't always clear once the sun's up — fog can linger until the ground warms or the wind picks up.

If visibility drops, slow down, leave extra space between you and the car ahead and stick to low beams. High beams bounce off fog and actually make it harder to see.

The cold-morning chain reaction

Fog is only one part of the disruption. The same cold conditions can create several problems at once:

Frost covers the windshield. Clearing every window and mirrors can add several unplanned minutes to your morning commute.

The dashboard lights up. Cold air contracts to reduce the tire pressure and trigger a warning light.

(MORE: Why does this warning pop up on your dashboard?)

The school commute gets darker. Shorter days place children, pedestrians and cyclists outside in darker conditions while fog makes them harder for drivers to see.

Fog conceals road hazards. It can hide stopped traffic, intersections, animals crossing and sharp curves.

Moisture freezes on cold roads. When pavement temperatures are at or below freezing, supercooled fog droplets can freeze onto roads and create a thin glaze of black ice.

(MORE: How cold temperatures affect the tire pressure)

Your first cold morning checklist

Check these conditions and have supplies ready the night before:

• Overnight low temperature
• Dew point and humidity
• Visibility forecast
• Dense-fog, frost or freeze alerts
• Tire pressure
• Windshield scraper or defroster
• Sunrise time and school-bus arrivals

(MORE: The best hack to defrost your car quickly)

Fall is not merely a signal to grab a jacket. Whatever that first cold morning throws your way — frost, fog or a tire light — budget in extra time and be ready for the impacts before you leave.

Faiza Mohammed is a meteorologist intern at weather.com. She studied geography and worked with the Weather Dawgs team at the University of Georgia. She also received her master's in Earth and Atmospheric Sciences from the Georgia Institute of Technology.