Heavy falls of snow may weigh down the young, tall trees to such an extent that they break.
Lightning--it is worst in the hills and mountains of the western states--may strike and damage a number of trees in the same vicinity.

If these trees are not killed outright, they are usually damaged so badly that forest insects and fungi complete their destruction.
Big trees are sometimes uprooted during forest storms so that they fall on younger trees and cripple and deform them.

Winds benefit the forests in that they blow down old trees that are no longer of much use and provide space for younger and healthier trees to grow.

Usually the trees that are blown down have shallow roots or else are situated in marshy, wet spots so that their root-hold in the soil is not secure.

Trees that have been exposed to fire are often weakened and blown down easily.
Where excessive livestock grazing is permitted in young forests considerable damage may result.