Mountain thunderstorms pose significant risks because of their consequences, especially for mountaineers, hikers and paragliders. Despite monitoring weather conditions to prevent accidents, disasters occurring during such phenomena often remain unpredictable and are the subject of novels or other stories.

Thunderstorms are formed when air in a layer of the atmosphere is unstable. A parcel of air raised at the base of this layer is then warmer than the environment and rises. In rising, its temperature decreases by adiabatic expansion, and when the relative humidity of water vapor reaches saturation, this forms a convective cloud. To form a storm, this layer must be very large and the temperature at the top of the cloud must be below −20C.

Mountains can help trigger atmospheric convection in three ways:

In a more general case, several effects may be present and if the synoptic wind is opposed to the anabatic wind, additional convergence occurs at the top of the mountain. It is also possible to create a convergence zone behind the mountain when the synoptic wind can divide and go around it to meet again (ex. Puget Sound Convergence Zone ) that will promote convection.

The uprising serves to not only destabilize the air and form convective clouds, but also to enhance its intensity. As the rising air from the bottom of the slopes is hotter and humid than the surrounding air, the lifted index will be more negative, increasing the vertical extension of the cloud . A simple temperature difference of 2C is enough to greatly aggravate the violence of thunderstorms.

Mountain storms have particularities because of the proximity of clouds, the importance of electric fields, their rapidity of appearance, their particular danger. Sudden wind lift of a mass of air can radically change the initial conditions within them.

Observable phenomena give an idea of the peculiarities of mountain storms .

Mountaineers are the most exposed to these phenomena, in ridges and pass passes.