The process of jump-starting a car in cold weather is the same as jump-starting it in any weather. In cold weather, however, the cold-cranking amps of the battery may be more compromised and, depending on how low or dead the battery is, will dictate how long the procedure will take.
Park the assisting car strategically so that the jumper cables can reach the batteries of both vehicles. Open the hoods of both cars. Leave the assisting vehicle running.
Attach the red clamp of the cables to the positive battery terminal on the assisting car. This has a "+" insignia stamped on the battery housing. Be sure that the jumper cable wires are clear and free from the moving parts of the running engine. Also, be sure that the other ends of the jumper cables do not come into contact with one another.
Attach the black clamp of the jumper cables to the negative battery terminal on the battery of the assisting car. This has a "-" insignia stamped on the battery housing.
Keep the remaining two clamps isolated from each other and approach the dead battery. Attach the red clamp to the positive terminal, and the black clamp to a non-moving metal bracket away from the battery. This is to ground the battery and prevent sparks from igniting any vapors near the battery that may be present.
Start the car. The amount of time charging the battery will take depends on how cold the weather is, how dead the battery was and how many cold-cranking amps it will take to turn the engine over. The size of the assisting car will be a factor, as well. Trying to jump-start a large engine with a small one is sometimes futile because the small car does not have enough cold-cranking amps to boost the engine-starting system of the larger vehicle. Revving the engine of the assisting vehicle might help, but the process may take time.
Remove the black clamp from the metal ground position in the car with the formerly dead battery first, and then remove the red clamp from the battery.
Remove the black clamp from the assisting car battery, then the red clamp. Close the hoods.
