About 745,000 crashes a year in the United States are weather-related, roughly 12 percent of all motor vehicle collisions, and they kill more than 3,800 people on average each year.1FHWA. How Do Weather Events Affect Roads? Driving in adverse weather and low visibility carries a specific set of legal duties: you must slow down to a speed that is actually safe for conditions, increase your following distance, use your headlights, keep your vehicle properly equipped, and in some places take extra steps like chaining up or clearing snow. Breaking any of those rules can bring traffic citations, points on your license, civil liability if you crash, and higher insurance premiums even if nothing is hit.
The Basic Speed Rule
Nearly every state has some version of what traffic attorneys call the basic speed rule. You may never drive faster than what is reasonable and safe for the conditions you’re actually facing, regardless of the number on the speed limit sign. A highway posted at 65 mph with fog cutting visibility to a few car lengths is not a 65 mph road at that moment. Maintaining the posted limit there is both dangerous and illegal.
What counts as reasonable depends on the road surface, how far ahead you can see, the traffic around you, and whether water, ice, or debris is on the pavement. The question courts and officers ask is whether your speed gave you enough distance to stop safely. A driver doing 45 on a fog-shrouded highway can still be cited for driving too fast for conditions if that speed exceeded what the environment safely allowed.
The posted limit is a maximum for ideal conditions, not a floor during storms. Pointing at the sign is not a defense.
Following Distance
On dry pavement, the standard advice is to leave at least three to four seconds between you and the vehicle ahead. In rain, snow, fog, or ice, federal safety guidance recommends doubling that gap.2Federal Motor Carrier Safety Administration. CMV Driving Tips – Following Too Closely Wet or icy roads can double or triple your stopping distance, and tailgating in those conditions removes any margin for the unexpected.
To measure your gap, pick a fixed object at the roadside and count the seconds between when the car ahead passes it and when you reach it. If you’re counting less than six or seven seconds in rain or snow, you’re too close.
Headlights and Visibility Equipment
Most states require headlights to be on during any period of reduced visibility, not only after dark. Around 18 states go further with “wipers on, headlights on” laws: if conditions are bad enough to run your wipers, your headlights must be on too. California’s Vehicle Code, for example, requires headlights during both darkness and inclement weather.3Justia. California Code Vehicle Code 24400 – Headlamps Even where no specific wipers-on statute exists, officers can cite you under general equipment or unsafe-vehicle laws if you’re invisible to other drivers in a downpour.
Headlights exist as much for other drivers as for you. Daytime running lights usually don’t activate your taillights, so they don’t substitute. Turn the full headlight system on.
High Beams Make Fog Worse
One of the most common mistakes drivers make in fog is reaching for high beams to see farther. Fog, heavy rain, and snow reflect that light back at you, creating a bright wall of glare that cuts visibility further. Use low beams in fog. If your vehicle has dedicated fog lights mounted low on the bumper, use them with your low beams. High beams belong on dark, clear roads.
Clearing Snow and Ice From Your Vehicle
No federal law requires you to clear snow or ice from your car before driving, and a significant number of states have no snow-specific statute at all. In those states, police rely on general traffic laws covering obstructed views, unsecured loads, or unsafe vehicles. You can still be cited if snow or ice blocks your visibility or flies off your roof into another vehicle.
A handful of states do have explicit snow-removal requirements, with fines starting as low as $25 for a basic citation and climbing to $1,000 to $1,500 when dislodged ice causes injury or property damage. Commercial vehicles often face steeper penalties. Clearing the entire vehicle — roof, hood, trunk, windows, mirrors, and light housings — is the only approach that keeps you and the drivers behind you safe.
Tires and Traction
Your tires are the only part of the vehicle touching the road, and tread depth determines how well they channel water out of the contact patch. NHTSA considers tires unsafe when tread wears down to 2/32 of an inch, the point at which traction drops off sharply on wet surfaces.4National Highway Traffic Safety Administration. Tires Federal rules for commercial vehicles are stricter, requiring at least 4/32 of an inch on front steering tires.5eCFR. 49 CFR 393.75 – Tires You can check tread at home with a penny: insert it into a groove with Lincoln’s head down, and if you can see the top of his head, the tire needs replacing.
Worn tires raise your risk of hydroplaning, the condition where tires ride on a film of water and lose contact with the pavement. Hydroplaning can start at highway speeds in moderate rain, and once it does, steering and braking are essentially useless until the tires regain grip.
Chain and Traction-Device Laws
In mountainous and northern states, chain or traction-device requirements are common in winter. They’re typically triggered by roadside signs, highway advisory systems, or seasonal date windows running roughly October through April. Some states use tiered alert levels: lower tiers may require chains only on commercial trucks, while higher tiers require them on any vehicle without four-wheel drive and snow-rated tires.
Fines vary widely, and penalties increase if your unchained vehicle blocks a lane or triggers a road closure. If you regularly drive in serious winter weather, carry chains that fit and practice installing them before you need them on a snowy shoulder.
Hazard Lights While Driving
Many drivers flip on their hazard lights during heavy rain, but the laws split. Some states permit hazard-light use while moving in low visibility; others prohibit it entirely and can issue a citation for it. The division is roughly even, and states keep updating their vehicle codes.
There are also real safety drawbacks. In most vehicles, activating the hazards disables the turn signals, so other drivers can’t see lane changes or turns. Flashing can mask whether you’re braking. And hazards normally signal a stopped or disabled vehicle, which confuses drivers approaching from behind who may expect you to be stationary. If visibility is bad enough that hazards feel necessary, the better move is usually to pull off the road entirely.
Rules for Commercial Drivers
Commercial drivers face an added layer of federal regulation. Under 49 CFR 392.14, drivers of commercial motor vehicles must use extreme caution when snow, ice, fog, rain, dust, or smoke reduces visibility or traction. The rule requires reduced speed, and if conditions become dangerous enough, the driver must stop and not resume until the vehicle can be operated safely.6eCFR. 49 CFR 392.14 – Hazardous Conditions; Extreme Caution The only exception is when stopping would put passengers at greater risk, in which case the driver may continue to the nearest safe location.
Hours-of-service rules include an adverse driving conditions exception. If a commercial driver meets unexpected bad weather after a trip has begun, they may drive up to two additional hours past their normal daily limit to reach a safe stopping point. The key word is “unexpected.” If the carrier dispatched the driver knowing a storm was coming, the exception doesn’t apply.7Federal Motor Carrier Safety Administration. How May a Driver Utilize the Adverse Driving Conditions Exception
What a Violation Costs
The most common weather-related citation is “driving too fast for conditions,” and it can be issued even when you were under the posted limit. Fines vary by jurisdiction, but the bigger financial hit comes from the secondary consequences. In most states these citations put points on your driving record, and accumulating points leads to license suspension and sharply higher insurance premiums. Insurers read a too-fast-for-conditions ticket as a signal that you lack situational awareness and price the risk accordingly.
Equipment violations stack on top of that. Non-functioning headlights, broken wipers, bald tires, or obscured taillights can each produce a separate citation. In severe cases an officer may pull the vehicle from the road until repairs are made. When behavior in bad weather crosses into reckless disregard for safety, such as weaving at high speed through a whiteout, the charge can escalate to reckless driving, with steeper fines, more points, and potential jail time.
Civil Liability After a Crash
Every driver owes a duty of care to everyone else on the road, and that duty requires behaving the way a reasonably careful person would under the same weather. Insurance adjusters and courts almost never accept “the weather was bad” as a defense. If you failed to slow for standing water, ignored ice you should have anticipated, or drove with fogged-over windows, you breached the duty.
The exposure grows if you violated a specific traffic statute at the time of the crash. Many states apply negligence per se, which treats a statutory violation as automatic proof of negligence. Driving without headlights in a rainstorm and rear-ending another car can establish your liability from the headlight violation alone. The other driver doesn’t have to prove you were careless; breaking the safety law is enough. Liability in weather crashes commonly covers medical bills, lost wages, property damage, and pain and suffering, and it applies regardless of intent.
When to Stop Driving
NHTSA’s standing guidance is blunt: if conditions are bad enough to make you uncomfortable, postpone the trip or pull over until conditions improve.8National Highway Traffic Safety Administration. Winter Weather Driving Tips: Prepare Your Vehicle If you can’t see the road markings, your vehicle is sliding on every curve, or you’re gripping the wheel with white knuckles, get off the road.
Pull completely off the travel lanes onto a shoulder or parking area. Turn on your hazard flashers so other drivers see you. Stay in the vehicle with your seatbelt on, because standing outside a car on a highway shoulder in low visibility is extraordinarily dangerous. Wait for conditions to improve and check traffic reports before pulling back on.