There is a lot of debate surrounding this topic, the overall consensus appears to be that hot water freezes faster than cold water. The “Mpemba effect,” named after Erasto Mpemba, a Tanzanian high school student who first noticed it in 1963, is an apparent natural phenomenon. When two bodies of water with differing temperatures are exposed to the same subzero environment, the hotter water freezes first, causing the Mpemba effect.