Lightning is caused by an electrical charge, which builds up between a cloud and an elevated object on the ground. Since there is a strong attractive force between positive and negative charges, lightning is very energetic, but unpredictable in its timing and effect.
Lightning can be attracted to the same object repeatedly, either during a single storm, or at another time. There are reports that a man was struck by lightning four times over a thirty year period! Tall buildings like the CN Tower in Toronto, or the Empire State Building in New York, are often struck by lightning. However, because they’re equipped with very large lightning conductors, the electrical charge is carried harmlessly into the ground.
The chances that a tree will receive a lightning strike depend mainly on its height. All trees attract lightning because they are tall and contain a lot of moisture, which provides good electrical conduction for the lightning. The belief that oak trees attract lightning more than other trees arises because they tend to be taller than surrounding trees, and they have a higher moisture content. A tree hit by lightning is more likely to survive if it’s soaked by rain, because much of the electrical charge is able to move safely down the outside surface moisture, instead of inside the tree.
So next time you’re out in a thunder storm lie low, avoid trees, and try to go inside a building.