It might seem absurd, but things at negative temperatures are actually "hotter" than things at positive temperatures (above absolute zero). If something with a negative temperature comes in contact with a positive-temperature object, heat will go from the negative object to the positive. This is because temperature is a trade-off between energy and entropy. If you add energy to a positive-temperature object, it will "increase" in entropy. If you add energy to a negative-temperature object, it will "decrease" in entropy.