Why won't my car start in cold weather?

Updated October 23, 20268 sources4 min read

Short answer

Most of the time it's the battery: cold slows the chemistry inside it, so it delivers far less power (AAA says about half its rated capacity at 0°F) just as cold, thick oil makes the engine harder to turn over, and batteries three or more years old are the most likely to give up. If the engine cranks normally but won't fire, the battery is fine and the problem is fuel or ignition, which is a job for a shop or roadside assistance.

Safety first. Never jump start or charge a battery that looks frozen, cracked, bulging or leaking; a discharged battery can freeze at 32°F and can burst. Don't let a car idle to warm up in a closed garage, because exhaust contains carbon monoxide. If it still won't start, call roadside assistance rather than cranking until the battery is flat.

On this page

Step by step
Why cold mornings are the hardest start
What the sound tells you
When it’s not the battery
Getting it started this morning
Stopping it from happening again
Follow-up questions
Sources

Step by step

1
Listen to what happens when you turn the key
Slow, labored cranking or rapid clicking points to the battery. A single click with bright dash lights points to the starter or a connection. Normal-speed cranking with no start means the battery is doing its job, so look at fuel and ignition instead. Nothing at all (no lights, no sound) is usually a dead battery or a loose cable.
2
Turn off everything that draws power
Switch off the headlights, heater fan, heated seats, rear defroster and radio, and unplug phone chargers, so all the battery's power goes to the starter. Firestone recommends this before every cold start.
3
Try in short bursts, not one long crank
Crank for a few seconds at a time and wait between tries so the battery recovers a little. Nissan's owner's manual says not to crank longer than 10 seconds at a time when jump starting. Grinding on for a minute wears out the starter and drains what's left of the battery.
4
Jump it or use a jump pack if it cranks slowly or clicks
Follow our jump-start steps (last clamp on bare metal, not the dead battery's post). First look at the battery; if the case is bulging, cracked or leaking, don't jump it.
5
Drive it at least 15 minutes afterward
Consumer Reports says to drive at least 15 minutes when you start a car that sits in the cold, so the alternator can put charge back in. A short trip to the corner store takes out more than it puts back.
6
Get the battery tested
A battery that needed a jump in the cold is telling you something. Parts stores and many shops will load-test it, and AAA says to test aging batteries every year. If it fails, replace it with one that meets or beats the cold cranking amps (CCA) your owner's manual lists.

Why cold mornings are the hardest start

Starting an engine is the biggest job a car battery does, and cold makes it harder from both sides at once:

The battery has less to give. Cold slows the chemical reaction that makes electricity. Sources put the loss differently, but all in the same direction: up to 35% of its power at 32°F (Caterpillar), up to 60% in freezing temperatures (Firestone), and about half its rated capacity at 0°F (AAA).
The engine asks for more. Cold oil is thick, so the engine is harder to turn over. AAA says an engine needs about 30% more energy to start at freezing.

A healthy, fully charged battery covers that gap. One that’s aging, partly drained by short trips, or already weak is the one that leaves you sitting in the driveway on the first hard freeze.

What the sound tells you

What you hear and see	Most likely cause	What to do
Slow, labored cranking	Weak or cold battery	Turn off accessories, try in short bursts, then jump it
Rapid clicking, dim dash lights	Battery too weak to turn the starter	Jump it or use a jump pack; get the battery tested
One click, bright lights	Starter or a loose or corroded connection	See our clicking guide
Nothing at all	Dead battery or a loose battery cable	Check the cables, then jump it
Cranks at normal speed, won’t fire	Fuel or ignition, not the battery	Check recalls, then call a shop or roadside assistance

When it’s not the battery

If the engine spins at normal speed and just won’t catch, more cranking won’t help and will drain the battery too. Possibilities in the cold:

Model-specific cold-start faults. Consumer Reports has documented cold no-start problems on particular models traced to frozen relays, PCV valves and fuel pumps, some fixed for free under manufacturer service bulletins. Check your VIN for open recalls and ask a dealer about bulletins for your model.
Ice in the fuel system. Gasoline doesn’t freeze in ordinary winter weather, but AAA says moisture in a low tank can form ice crystals that clog the fuel filter. Keep the tank at least a quarter full before a deep freeze.
Diesel gelling. Diesel fuel can gel near or below freezing (Caterpillar). Winter-blend fuel and a block heater prevent most of it.

Getting it started this morning

Turn off every electrical load and unplug chargers.
Crank in short bursts with a pause between; don’t grind on it.
If it cranks slowly or clicks, jump it or use a jump pack. Our jump-start guide has the clamp order. Look at the battery first: if it’s bulging, cracked or leaking, don’t jump it.
Once it starts, drive at least 15 minutes (Consumer Reports) instead of idling in the driveway. A long warm-up idle doesn’t help; see how long to warm up a car in winter.
Get the battery load-tested that week. If it needed a jump once, it’ll likely need one again on the next cold morning.

Stopping it from happening again

Replace an old battery before winter. Firestone says batteries three years or older struggle most in the cold; AAA puts typical life at three to five years and says to test aging batteries every year. If yours keeps going flat even when it’s not cold, see why a battery keeps dying.
Buy for your climate. AAA and Firestone both say to choose a battery with a cold cranking amps (CCA) rating that meets or beats your vehicle maker’s spec.
Park out of the cold in a garage or out of the wind when you can.
Drive it, and drive it long enough. Firestone and Jalopnik both warn that short trips and cars that sit for days leave the battery undercharged.
Warm the engine or battery where it regularly gets very cold: a block heater or battery blanket means the battery has less work to do (Jalopnik, Firestone).
Unplug accessories like dash cams and phone chargers when the car is off; Jalopnik notes some outlets keep drawing power after shutdown.

Common follow-up questions

Why does cold weather kill car batteries?

Two things happen at once. The chemical reaction that makes electricity slows down, so the battery can deliver less power: AAA says about 50% of its rated capacity at 0°F, Caterpillar says a battery at 32°F can lose up to 35% of its power, and Firestone says up to 60% in freezing temperatures. Meanwhile, cold engine oil is thicker, so the engine takes more effort to turn; AAA says an engine needs about 30% more energy to start at freezing. A healthy battery covers that gap. A weak one doesn't.

My battery was fine yesterday. Why is it dead today?

Cold doesn't usually ruin a good battery overnight; it exposes one that was already weak. Firestone says batteries three years old or older struggle most in the cold, and AAA puts typical battery life at three to five years. Short trips, a car that sits for days, and accessories that draw power with the engine off all leave the battery partly charged going into a cold night.

The engine cranks normally but won't start. What's wrong?

If it spins at its normal speed, the battery is doing its job. The cause is more likely fuel or ignition: Consumer Reports has reported cold-start problems on specific models traced to frozen relays, PCV valves and fuel pumps, some covered by free manufacturer repairs. Check for open recalls by VIN, and if that's clear, have a shop or roadside assistance look at it rather than cranking until the battery dies too.

Can gas freeze in my car?

Gasoline itself doesn't freeze in normal winter weather; AAA says it freezes somewhere between about -40°F and -200°F depending on the blend. Moisture in the air inside a near-empty tank can freeze into ice crystals, though, and AAA says those can clog the fuel filter. Its advice is to keep the tank at least a quarter full before a big temperature drop.

Why won't my diesel start in the cold?

Diesel fuel can gel when it sits near or below freezing, which thickens it and clogs the filter. Caterpillar recommends winter-blended diesel, draining water from the fuel filter so it doesn't freeze overnight, and a block heater so the engine is easier to start. Caterpillar also lists glow plugs and air inlet heaters among the parts to check before winter. A diesel that has already gelled is usually a shop or roadside job.

How do I keep my car from not starting when it's cold?

Replace a battery that's old or tested weak before winter, and when you do, pick one that meets or beats the CCA rating your manual lists. Park in a garage or out of the wind when you can, drive at least 15 minutes at a time, and unplug accessories when the car is off. Where it regularly gets very cold, a battery blanket or an engine block heater helps: a warm engine needs less battery power to start.

Do hybrids and electric cars have this problem?

Yes, in a different way. Hybrids and EVs still have a small 12-volt battery that powers up the car's computers, and if that battery is weak the car won't turn on even with a full high-voltage battery. It can be jump started on its 12-volt jump points the same way; see our jump-start page. Cold also reduces an EV's driving range, which is a separate issue from starting.

Sources

General information only, not a diagnosis. Your owner’s manual comes first. How we write these