Seriously, at 2 AM, when there is no water running through your pipes, it’s really unlikely that it’s the water pipes making the sound. All of the responses so far seem to have followed your lead, and tried to explain why the pipes are creaking. In Vegas? During a summer night? If it’s not the toilets running, it probably has nothing to do with water unless there’s a leak. Water hammer is a result of moving water, as is the clicking that some older meters can cause. Thermal creaking is the result of rapidly changing temperature. All highly unlikely at 2 AM.
