From the Bigfoot Diaries:
Sasquatch Migration in Washington State? Sasquatch sightings and encounters have been occurring in and around the caves of Washington State. These extensive caves and underground tunnel systems were caused by volcanic eruptions and lava flows which occurred thousands of years ago. The hundreds of cave systems in Washington differ greatly between the western and eastern regions of the state. The western half of the state is very wet and covered in thick lush forest while the eastern side of the state is a dryer, more arid climate.Some theories suggest that the Sasquatch may migrate west to east during the fall and early Winter. The numerous underground and above ground cave systems could be a way for the Sasquatch to migrate unnoticed. The eastern side of the state is too warm for the Sasquatch during the summer. The dense cool forests that cover the western side of the state provide an optimal environment for the Sasquatch to thrive during the spring, summer and fall.