In some circumstances, warmer water can freeze faster than colder water. There are records of this from as far back as Aristotle's time. In modern times, this counterintuitive property has been named the Mpemba effect, after Erasto Mpemba, a Tanzanian secondary school student who re-discovered this phenomenon back in 1963.
It's one of those cases where just because we know something happens, doesn't mean we entirely understand why. But the process of scientific speculation is still interesting.