While lightning cannot strike you directly if you’re inside your house, it can travel through wires and other conductive surfaces that lead into the house. If you happen to be in contact with one of them, it’s possible you could can get electrocuted.
In addition to outdoor fatalities caused by lightning, a number of people are injured indoors every year, including individuals who are using their landline telephone during a thunderstorm (Source: Medscape).
Lightning is a master of trickery and can do some pretty strange things. But, the odds of you being struck by lightning while inside a building are considerably less than winning the Powerball lottery.
However, houses do have a lot of internal wiring. There is solid gauge copper wire leading to every wall outlet and light switch. Copper telephone lines run to every phone jack. Coaxial cables run from your satellite dish or cable provider to wall jacks. Most of these conductive wires start at some distribution point outside your house such as a utility pole or a satellite dish. If lightning happens to strike nearby, it’s possible the electricity could find it’s way inside your house by traveling along those wires.
It’s also possible the lightning might directly strike the house, then arc flash onto the conductive copper wires. If the house’s grounding system is broken or inadequate, the electricity may have to travel even further to find the ground. If you happen to be on a landline phone, you could get a jolt right to the head!
Conductive copper pipes providing city water also run into each house, but they are buried underground. Moreover, most newer houses use Plex tubing made of plastic which is not conductive. So the risk of electrocution while taking a bath or shower is much lower these days.
Interestingly, the iron gas line coming into your house are also conductive, but like the copper pipes, they are buried underground. In 2019, a lightning strike did hit a tree severing a gas line outside a home which resulted in a small fire (Source: CTV News Canada). The good news is, I have yet to read any article of a house blowing up due to a gas line being struck by lightning.
When I lived in North Carolina, the homeowners right behind us had their house struck by lightning. It went right through the top of their asphalt shingled roof creating a 2×2 foot hole. The electricity from the lightning strike arc flashed to the wiring in the attic, ruining just about every electrical appliance plugged into an outlet. The wiring inside the walls vaporized, blowing out chunks of drywall and left black acrid scorch marks in their place.
Here is a link to some pictures of another house unlucky enough to be struck by lightning.
Just remember, one of the safest places to be during a thunderstorm is in your house. The odds of being struck by lightning while inside are extremely low. If you happen to live in a part of the country that experiences a lot of lightning strikes, a good investment might be some sort of lightning protection device such as a properly grounded lightning rod or surge arrestor. This will help the electricity from a lightning strike harmlessly find the ground.