Thunderstorms and lightning

A thunderstorm is defined as a violent atmospheric disturbance characterized by lightning and thunder within a huge cumulonimbus cloud (see image). 

Thunderstorms are born of atmospheric instability produced by the meeting of a warm, moist air mass and a cold air mass. They are considered convective systems; that is, a system characterized by vertical movements in the atmosphere, in which instability rapidly creates strong upward and downward movements. 

In cumulonimbus clouds, conditions are ideal for intense precipitation, strong gusts of wind, and sometimes hail. Thunderstorms are phenomena that are generally highly concentrated in space and time, and the intense precipitation they produce is short-lived.  

The occurrence of thunderstorms in Quebec


The mechanisms that cause air masses to meet are what cause thunderstorms to arise in a particular place and even depending on the time of day. On one hand, thunderstorms are often found along a cold front accompanying a meteorological low-pressure area. These lines of thunderstorms can sweep across several regions in succession, occurring at any time of day and in any season, although they are very rare in winter. 

On the other hand, the hot, humid summer days typical of southern Quebec are conducive to the formation of late afternoon and early evening thunderstorms. This type of summer thunderstorm is often very localized and ceases as the sun sets.  

Generally speaking, southern Quebec is characterized by a greater number of thunderstorms, which gradually diminish as you move northwards. As a result, most regions experience thunderstorms every year. However, this is not necessarily the case for far northern regions like Nunavik. 

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