Lightning effects?

How can I create a light that flickers like lightning? I’m making an FPS Horror game and I want to create the effect of lightning flickering outside a window. Also, this will be the ony light source in some rooms. Please help me.

You can make a few 3D models of sparks and replace them every frame randomly and with random rotation, obviously with an emitting shader.
You may then add an halo around a blue-ish point light source and make it change randomly it’s radius.
And finally you may add particles to simulate little sparkles.