What is the state of butane at -150 degrees?

At -150 degrees Celsius, butane would be in a solid state. Butane has a melting point of approximately -138 degrees Celsius, so at -150 degrees, it is well below this temperature, causing it to crystallize. In this solid form, butane would not be usable as a fuel or in typical applications where it is usually found as a gas or liquid at higher temperatures.