Where does the heat wave come from?


If it is warmer than 25 degrees Celsius for five consecutive days in Uccle, of which three days will be more than 30 degrees, we speak of a heat wave. The RMI predicts high temperatures for the rest of the week, but where exactly does that heat come from?

Last summer, our country had no less than three heat waves, at the end of July even record temperatures of more than 40 degrees were recorded. This year the month of July was fresher than average, but this week, if the predictions are correct, we will experience the first heat wave of 2020.

The RMI expects more than 25 degrees on Wednesday and 30 degrees or more by Thursday. Saturday in particular could turn into a tropical warm day, with 35 degrees in the shade. Sunday and the following days are not immediately expected to cool down, fulfilling the conditions for a heat wave. Rain also does not seem to be imminent. For example, 2020 can become the sixth year in a row that a heat wave is occurring in our country.

Dry soil, warm air

Where does this heat wave come from? “Warm air always comes from the south,” says weatherman David Dehenauw. The following days our country will receive warm air from France and Spain. At present there is a high pressure area in Central Europe, Belgium is located on its western flank.

The air will also be extra warm, because the bottom is dry. “The heat is normally distributed between the evaporation of the soil and its warming,” explains Dehenauw. ‘But the less water there is in the soil, the faster the soil heats up. The air that comes into contact with the soil therefore heats up faster. ‘

Seek coolness

Such heat is not good for your health and can cause dehydration, cramps or even a heat blow. The Interregional Cell for the Environment (Ircel) has activated the warning phase of the ozone and heat plan. Sun and high temperatures, combined with air pollution, can increase ozone concentrations. It is not recommended to make heavy efforts, such as outdoor sports. It is important to drink enough, to keep yourself and your house cool, and to ensure that children or the elderly in the area also find sufficient drinking and coolness.

According to the Agency for Care and Health, extra attention is needed this year for people who are weakened by the new corona virus. They can be extra vulnerable to heat-related diseases. Conversely, people with heat stress are extra vulnerable to Covid-19.

The heat is not good news for the groundwater levels in our country, which are already low in many places in Flanders, because too little rain has fallen in recent years. Four hundred liters in three years to be precise, says Dehenauw. You don’t make up for that any time soon, even if it were going to be a wet autumn.


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