The best place to be during a thunderstorm is inside a safe building - one that is fully enclosed with a roof, walls and floor. But safety precautions should be taken inside as well.
Small open shelters offer no protection from lightning. Only shelters that contain plumbing or wiring throughout, or some other mechanism for grounding from the roof to ground, are safe during thunderstorms.
But remember, while wiring provides safety due to grounding, areas with wiring should not be touched as lightning can travel through them - and that includes electrical, phone, radio, television and computer systems. Phone use during thunderstorms is the leading cause of indoor lightning injuries in the United States.
Lightning generates electrical surges that can damage electronic equipment, even if it is some distance from the actual strike. Typical surge protectors will NOT protect equipment from a lightning strike. You may want to unplug valuable electronic equipment before the storm arrives.
Lightning can travel through metal wires or bars in concrete walls or flooring and through plumbing systems, including shower heads and faucets.
For additional lightning safety information, visit the NOAA Lightning Safety webpage.