I sit by a west-facing window at work. Can lightning travel through the window?
— Mary Anne Freeman
It's highly unlikely that lightning would enter a building through a window, regardless of the direction the window faces or whether it is open. That said, the electric current from a lightning strike near or directly to a building can enter the building from pipes in the ground or through metal plumbing pipes and wiring. Lightning expert Dr. Martin Uman writes, “If the particular conductor in which the current is traveling is not well connected to the ground, the lightning may choose to leave that conductor and jump through the air to what it regards as a better path to the ground. The trip through the air, or side flash, accounts for a significant fraction of indoor lightning fatalities.”