Cold golf balls do not go as far when struck. If you leave your golf balls outside in severely cold weather, several methods can be used to warm them up prior to play, and keep them warm during play, so you can receive maximum performance. Keep in mind using equipment in an unusual manner is against the United States Golf Association's Rules of Golf. Carrying heated golf balls with you during play falls into that category of "unusual manner."
Place a pot of water on the stove. The pot should be big enough to accommodate all the balls you want to heat plus at least 2 quarts of water.
Heat the water until it reaches 120 degrees Fahrenheit. That's not scalding hot. Hot tap water can reach 125 degrees. Test the water's temperature with a meat or candy thermometer.
Put a folded towel on the bottom of the pot. Push it down into the water with a spatula or spoon. Put the golf balls in the hot water on top of the towel. The towel keeps the balls from touching the hot metal on the bottom of the pan. Increase the heat until the water reaches 120 F and remains there. Leave the balls in the water for 30 minutes.
Remove the balls from the water. Dry them and place them in an insulated food bag to help retain the heat. Keep the bag in the car as you drive to the course. Reseal the bag each time you remove a ball.
Select hand warmers that use a chemical reaction to generate heat. Put one activated hand warmer on the bottom of an insulated food bag.
Put the balls on top of the hand warmer. Place another activated hand warmer on top of the balls.
Close the food bag tightly around the warmers and the balls. The balls should be warm after 30 minutes. Replace the hand warmers when they cool off if you haven't finished your round of golf.