Water freezes at 32 degrees Fahrenheit (0 degrees Celsius) . However, scientists have found liquid water as cold as -40 degrees Fahrenheit in clouds and even cooled water down to -42 degrees Fahrenheit in the lab. When liquid water is cooled below -42 degrees Fahrenheit, it crystallizes into ice too quickly for scientists to measure the temperature of the liquid. Ocean water freezes at about 28.4 degrees Fahrenheit because of the salt in it.