Small meteorology: This creates a thunderstorm

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Throughout the day an ever more oppressive humidity, then suddenly dark clouds form, the wind freshens up - and a thunderstorm arises. So welcome in the summer the rain is for the garden, so feared is the destructive power of heavy downpour, storm and hail.

When exactly it crashes, remains exciting in spite of modern technology and weather forecasts, because thunderstorms discharge mostly very small-scale. While the basements are full of water in one place, fall a few kilometers hardly a few drops. In addition to the weather, the shape of the terrain also plays a role: In the mountainous region, thunderstorms occur more frequently because the air masses are forced to ascend. In the truest sense out of the blue the storms can break over the hiker. In the lowlands, on the other hand, thunderstorms start earlier: the sky is darkening, air pressure and temperature are falling, but humidity is rising.

This creates heat or front storms

Air currents during heat storms

Air currents in the front storm

During the thunderstorm (left), a strong temperature gradient between cold mountain air (blue) and moist air near the ground (red) leads to a rapid exchange of air between altitudes, often accompanied by a temporary drop in temperature and strong gusts of wind. From the condensation of the cooling warm air, the typical high storm cloud forms. Between the opposing air currents creates a strong friction through which the cloud is electrically charged. In the front storm (right), cold air masses move under the hot air close to the floor, and an electrical charge also takes place at the interface

Heat storms are also known as convection storms. They occur mainly in the summer, often in the afternoon or evening. The sun heats the air above the ground, it absorbs moisture. If the air is much cooler at higher altitudes, the moist, warm ground air rises. It cools down, the contained water condenses and clouds form. Impressive cloud mountains (Cumulonimbus clouds) tower up to ten kilometers high. In the clouds blow strong upward and downward winds. Electric charges arise, which are discharged by lightning.
In front storms, hot and cold front meet. The colder, heavier air pushes under the lighter warm. As a result, it cools down, water vapor condenses and a thundercloud emerges as in a heat storm. In contrast to this front storms can occur year round and are often accompanied by a drop in temperature and weather changes.

Estimate the distance to the storm

To estimate the distance to a thunderstorm, helps an old rule of thumb: offense between lightning and thunder three seconds, the thunderstorm is about a kilometer away. If it moves on, the gap between thunder and lightning gets bigger: If it comes closer, the same applies vice versa. Already ten kilometers away - about 30 seconds between lightning and thunder - threatens the danger of lightning strikes. Protective measures in the garden should therefore be avoided and better start the retreat into the house.


From the time between lightning and thunder, the distance to the storm can be estimated. Every second corresponds to about 340 meters

Thunderstorm damage due to hail and heavy rain

Large hailstones and heavy rain usually cause more damage than lightning strikes. In the ups and downs of the storms, which prevail within the storm cloud, ice crystals are whirled up and fall down again. Layer by layer, new freezing water settles on the outside of this cycle. Finally, when the ice lumps become too heavy, they fall out of the clouds, reaching speeds of up to 50 kilometers per hour or more, depending on their size. The stronger the storm and the prevailing winds, the heavier the hailstones may become. Worrying is the fact that storms with hail have increased in recent decades. A trend that will increase as climate change advances, researchers predict.


Hailstorms can have devastating effects, especially if the grains are large. They kill fruit or leaves or injure them, so that fungal diseases have easy play. But many plants recover surprisingly fast

When the storm has finally cleared and you have managed to get away without any damage except for a few fallen potted plants, you are grateful for the cleansing power of the storm: the air has cooled and clear, the sultriness has disappeared - and the garden is already watered.

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