> **Quick Answer:** Cold weather kills batteries faster than anything else, and that is the most likely reason your car won't start. Try a jump start first. If the engine cranks slowly or clicks but won't fire, a weak battery is the culprit. If it cranks fine but won't run, you're looking at a fuel or ignition issue. Below is what to check and in what order.
## Why Won't My Car Start After Sitting in the Cold?
A dead or weakened battery is responsible for the large majority of cold-weather no-starts. Cold temperatures slow the chemical reaction inside a lead-acid battery, which cuts the cranking amps it can deliver. A battery that was borderline in October may completely fail to turn your starter in January.
Here's the quick diagnostic by what you hear:
- **Nothing, or one click:** Dead battery or bad starter connection.
- **Rapid clicking:** Battery has some charge but not enough to crank.
- **Slow, labored cranking that won't fire:** Battery is weak, or oil thickened by cold is making the engine hard to turn.
- **Normal cranking but won't start:** Fuel delivery problem, a frozen fuel line, or a flooded engine.
If you're hearing clicking, the [car won't start clicking noise in cold weather](/car-wont-start-clicking-noise-cold-weather/) breakdown will walk you through the exact cause.
## How Do I Get It Started Right Now?
Jump start it first. That is your fastest fix if the battery is the problem.
1. Get jumper cables and a running vehicle, or a portable jump starter pack rated at 1000+ cranking amps for most gas engines.
2. Connect red to the dead battery positive terminal, red to the donor positive, black to the donor negative, black to an unpainted metal ground on your car (not the dead battery negative terminal).
3. Run the donor car for two minutes, then try to start yours.
4. If it starts, drive for at least 20 minutes so the alternator can recharge the battery. Don't make short trips or the battery won't recover.
If the jump start fails, or the car starts and then dies again within a day, the battery is done. A battery that fails below about 12.0 volts at rest and can't hold a charge after jumping needs to be replaced, not recharged. Most auto parts stores will test it free.
If you're stuck somewhere and can't get a jump, see [dead battery no jumper cables: your options right now](/dead-battery-no-jumper-cables-options/) for alternatives.
## Could It Be Something Other Than the Battery?
Yes, and here are the other cold-weather culprits worth knowing.
**Thick engine oil.** In extreme cold, conventional motor oil thickens and makes the engine harder to crank. If your vehicle calls for 5W-30 but you're running 10W-30, it compounds this. Switching to the manufacturer's recommended viscosity, or a full synthetic, helps significantly.
**Fuel system issues.** Moisture in your fuel tank can freeze in the fuel lines when temps drop hard. If the engine cranks normally but won't fire and the battery is fine, a bottle of fuel-line antifreeze (isopropyl alcohol based, products like HEET in the yellow bottle) added to the tank can clear a frozen line. This is more common in older vehicles and diesels.
**Diesel gelling.** Diesel fuel can partially solidify in temperatures below around 10 to 15 degrees Fahrenheit. If you drive a diesel and it won't start in extreme cold, standard j
*Photo: Pexels*
ump starting won't help. You need anti-gel additive or a heated environment.
**Flooded engine.** If you cranked repeatedly before reading this, you may have flooded the engine with raw fuel. Hold the throttle to the floor and crank for 10 seconds. That clears excess fuel. Then release and try a normal start.
## When Is It Time to Call a Tow Truck?
Call a tow if the jump start fails twice, if the car starts and immediately stalls, or if you hear grinding from the starter (possible starter motor failure). Continuing to crank a car that won't fire can overheat the starter motor and create a second problem on top of the first.
Also call a tow if you're in an unsafe location, if temperatures are dangerously low, or if the vehicle is a diesel with gelled fuel. A diesel with gelled fuel needs to be brought somewhere warm, not just jumped.
Before you call, check whether your insurance or a membership covers it. [Does insurance cover towing if your car breaks down (not an accident)?](/does-insurance-cover-towing-if-car-breaks-down-not-accident/) covers exactly this situation, since a cold-weather no-start is a mechanical breakdown, not a collision.
If you have a [car battery died in cold weather situation](/car-battery-died-in-cold-weather-jump-start-vs-tow/), that article compares the costs and trade-offs of jumping versus towing directly.
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*Photo: Pexels*
## Common Questions
**Q: How cold does it have to be for a car battery to fail?**
A: A fully charged battery in good condition can handle well below zero Fahrenheit, but a battery that is already weak or more than three years old can fail at temperatures as mild as 20 degrees F. Cold does not kill good batteries, it exposes the ones that were already going.
**Q: My car started fine yesterday, why won't it start today after a cold night?**
A: Overnight cold can be the difference between a marginal battery limping through and one that can't crank at all. If the temperature dropped 20 or more degrees overnight, that drop likely pushed a weak battery past its limit. Have it tested.
**Q: Can I damage my engine by trying to jump start it in the cold?**
A: Jump starting itself is not harmful if you connect the cables correctly. The risk is to your starter motor if you crank repeatedly without the engine firing. Limit each crank attempt to about 10 seconds, wait 30 seconds between tries, and stop after three failed attempts.
**Q: How do I keep my car battery from dying in cold weather going forward?**
A: Keep the battery terminals clean and tight, replace any battery older than four years before winter, and if the car sits for more than a few days in extreme cold, use a battery maintainer (trickle charger). Parking in a garage, even an unheated one, makes a measurable difference.
**Q: My car won't start and it's making no sound at all, not even a click. What's wrong?**
A: Complete silence usually means the battery is entirely dead, a cable connection is loose or corroded, or a fuse has blown. Check that the battery cables are tight at both the battery and the chassis ground. If they are secure and you get nothing, the battery is likely fully discharged and will need a jump or replacement.
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Car Won't Start After Sitting in Cold Weather: What's Wrong and What to Do
Photo: Pexels