Is there thunderstorm in winter?
One of the most common assumptions about thunderstorms is that lightning strikes most often in summer.
That is true, but we must still weigh that answer.
Thunderstorms are not only present in summer, thunderstorms also strike throughout the year..
What we call winter in meteorology covers the months of December, January and February, the coldest period of the year in the northern hemisphere1
How often do thunderstorms occur?
As noted earlier, thunderstorms are very common in the summer.
Compared to other seasons in Western Europe2, the proportion of lightning flashes in summer is 66%, whereas in winter it is only 2% (16% in spring and 16% in autumn)
However, the few thunderstorms that occur in winter should not be underestimated, as winter thunderstorms are the most violent thunderstorms in Western Europe.
The proportion of lightning flashes we will call “very violent3” (above 100 kA) is 58% in winter, compared to “only” of 9% in summer (and 10% in spring and 23% in autumn).
What is the difference with summer thunderstorms?
As a reminder, in a previous article we mentioned the conditions for convection: Thunderstorms form when the air mass is said to be unstable. That is, when there is hot air near the ground and cold air at altitude.
In summer the thunderstorms are called “hot air mass” with a mass of air made unstable by very hot low-lying air and humidity.
In winter, however, the conditions that must be met for a thunderstorm are very cold air at altitude that conflicts with the soft (or hardly fresh) air in low layers.
An example in France with the comparison of lightning density and amplitude, in summer and winter season.
You can notice that violent thunderstorms (>100kA) are more common in winter, although there are fewer thunderstorms.
>> Focus: The Mediterranean episodes.
Characterized by their sudden onset and high precipitation, the Mediterranean episodes are violent stormy systems, often causing localized flooding.
Good to know :
- They occur on average 3 to 6 times a year
- They are mainly located in the Mediterranean regions
- Their formation is observed in autumn, the period of the year when the temperature of the Mediterranean Sea is the warmest, which boosts the evaporation process. Hot, humid, and unstable air flows from the Mediterranean and northwards, where cooler air flows during this period, especially in the relief areas. This confrontation generates violent, localized thunderstorms (so-called “stationary cells”), accompanied by, more or less, intense rainfall depending on the observed thermal amplitude.
To learn more about Mediterranean episodes, consult the Météo-France file (in french).
No matter the season, summer or winter, you should be vigilant in the approach of a thunderstorm and not underestimate the violence of a thunderstorm in any season and in all latitudes …
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2Western Europe currently covers the following countries: France, Spain, Portugal, United Kingdom, Ireland, Belgium, Luxembourg, Netherlands, Denmark, Germany, Switzerland, Italy.
3The average amplitude of a lightning flash is 20kA