Why thunderstorms make the air feel so oppressive

Humid air prevents the body from cooling efficiently, making thunderstorms feel particularly exhausting, Yle reported on Friday as the Finnish Meteorological Institute warned of strong thunderstorm gusts across the country.

“Moisture cannot evaporate from the skin in the same way as it does in drier air. The body does not have time to cool down,” said Joanna Rinne, a meteorologist at Forecasta.

Humidity can cause discomfort and headaches, particularly among people with migraines. Research suggests that any change in weather can trigger a migraine, but a link between low pressure and headaches has not been established.

People with chronic illnesses, older people and those in generally poorer health are especially vulnerable to hot and humid conditions, Rinne said.

The heavy feeling before a thunderstorm is not caused by the weight of the air mass. It is caused by the high amount of moisture, or water vapour, in the air. Water vapour is invisible but can be felt on the skin.

Warm air can hold more moisture than cold air. Warm and humid weather is typical in Finland from mid-July to mid-August, Rinne said. Cold air can also have relative humidity close to 100 percent, but it contains much less water.

Rinne advised people to avoid strenuous exercise if the conditions feel particularly uncomfortable, to adjust their activity according to how they feel and to drink enough water.