What causes lights to flicker, or dim for a few seconds, during a strong thunderstorm?

Question

What causes lights to flicker, or dim for a few seconds, during a strong thunderstorm?

Answer 1

Lightning hitting part of the electric grid.

Answer 2

Electrical and magnetic interference is known to cause light flickering. When lightning strikes near a power station or any place controlling electric current supplied to buildings, the magnetic field created by lightning as well as its high current causes disturbances in the alternating current that is supplied to homes and so on. Alternating current commonly operates at 60 Hertz (cycles per second) and 120 Volts, but lightning causes the current to behave differently. AC that operates at 60 Hz does not allow someone to notice 60 flickers a second. When the current suddenly slows down or stops, you notice the flickers.