Car won't start in cold weather: why, and how to avoid it

Switch everything off. Then try, briefly.

The answer in 2 lines. Cold cuts the current a battery can deliver, just as a cold engine needs more effort to turn over. A battery that is already tired often gives up on the first frosty morning. Switch off every accessory, don't keep cranking the starter, and if it still won't go, jump start it following your handbook or call your breakdown cover. Have the battery tested before winter, especially if it is more than four or five years old. And before you drive off, clear all the ice and snow from the windows, lights and number plates: the Highway Code requires it.

The 4 steps to start

Switch everything off: headlights, heater fan, heated screen and seats, radio. All the power should go to the starter.
Manual gearbox: press the clutch down while starting, if your handbook says so; automatic: in P.
Diesel: wait for the glow plug light to go out before turning the key or pressing start.
No more than about 10 seconds per attempt, then wait about a minute before trying again. After three or four failures, stop: jump start with leads or a jump starter following your handbook, or call your breakdown cover.

Stop: danger

A battery that is swollen, cracked, leaking or frozen: don't charge it and don't try to jump start. Have it replaced.
No flames, no smoking, no sparks near a battery: it can give off a gas that catches fire or explodes.
Hybrid or electric car: follow the handbook only, or call your breakdown cover. They also have a small 12-volt battery that can go flat in the cold.

Why the cold kills batteries

A battery works through a chemical reaction that slows down in the cold: it delivers less current.
At the same time, cold engine oil is thicker: the starter has to work harder.
In winter we drive with lights, heater and heated screen on, often on short trips: the battery doesn't recharge properly.
A worn battery still copes in autumn, then fails at the first hard frost. Breakdown firms expect a surge of call-outs on the first working days of January, after many cars have sat unused in the cold over Christmas (Green Flag forecast 28,400 breakdowns for the first Monday back to work in January 2026).

It isn't always the battery

The starter turns slowly, dashboard lights dim: a battery weakened by the cold, or worn out.
The engine turns normally but won't fire, diesel: glow plugs, or diesel that has thickened (waxed) in a severe frost. Call your breakdown cover rather than adding products to the tank.
Nothing happens, dashboard lights bright: the starter motor or the immobiliser: see our battery or starter guide.
Doors or locks frozen: not a battery fault. Use a lock de-icer, never hot water.

Preventing it

Have the battery tested before winter, especially if it is over four or five years old or starting is getting slower. Many garages and fast-fit centres test batteries, sometimes for free: ask.
Park under cover when you can: garage, covered car park.
Avoid lots of very short trips; now and then, take a proper drive of half an hour or more.
Keep in the boot: jump leads in good condition or a charged jump starter, gloves, an ice scraper, de-icer, a torch and your handbook. Choosing: jump leads long and thick enough for your engine size; a jump starter rated for petrol or diesel and your engine size, as stated on the box.
Not driving for weeks? A smart battery charger or maintainer keeps the battery topped up. Check it suits your battery type (standard, AGM or EFB, often printed on the battery).

What not to do

Cranking the starter for a long time: you drain the battery and can damage the starter.
Pouring hot water on the windscreen or lock: the glass can crack, and the water freezes again straight away.
Leaving the engine running unattended on the road to warm up: it is an offence under the Road Vehicles (Construction and Use) Regulations 1986, and an easy car to steal. Idling recharges very little anyway.
Driving off with only a peephole cleared in the ice.

In England: breakdown cover, the law and your rights

Breakdown cover: check whether yours includes "home start" or "at home" cover: basic roadside cover often doesn't help if the car won't start outside your house. It is sometimes included with a bank account or car insurance: look before you buy a policy. How to choose: home start included, the number of call-outs allowed, recovery to a garage or home, and cover for the car or for you in any car. Which? compares providers: Which? — How to buy the best breakdown cover.
The Highway Code (rule 229): before you set off, you must be able to see. Clear all snow and ice from every window, and make sure lights, mirrors and number plates are clean.
A new battery that fails: under the Consumer Rights Act 2015, you can reject faulty goods within 30 days for a full refund; after that, ask for a repair or replacement. Citizens Advice explains the steps: Citizens Advice — Something's gone wrong with a purchase.
Old batteries never go in the bin: see our flat battery guide for where to take them.

The figures (latest published)

About half a million battery failures: Green Flag (Direct Line Group) said in November 2025 that it expected around half a million battery failures over winter 2025/26. It is a forecast by a breakdown provider, not an official statistic; figures for winter 2026/27 are not yet published.
10 seconds: the usual maximum for one starting attempt (follow your handbook).
30 days: the short-term right to reject a faulty new battery for a refund (Consumer Rights Act 2015).

Good to know

Emergency on the road, or someone in danger: call 999. Note your breakdown provider's number in your phone now.
The Highway Code also applies in Scotland and Wales; Northern Ireland has its own version with very similar rules.

In Durham, on a morning at minus 6°C, Liam's car clicks once, then nothing. He switches everything off, waits a minute, tries again without luck. Rather than keep cranking, he calls his breakdown cover, which includes home start. The patrol gets the car going and tests the battery: six years old and at the end of its life. Liam has it replaced that day.

A made-up story, for illustration.

Bobby

Sources, verification, confidence

Verified on 1 November 2026, for England. Confidence: high for the starting steps and the safety warnings (RAC); high for Highway Code rule 229 and the Consumer Rights Act 30-day rule; medium for the half a million battery failures, a breakdown provider's forecast for winter 2025/26, not an official statistic; medium for what breakdown cover includes, which varies by provider. Always follow your car's handbook first. This guide describes common cases, not a diagnosis.