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It will be hot, even very hot at the weekend. Whether it’s a heatwave depends mainly on the definition.
Over the past few days, local temperatures in Spain have reached temperatures above 40 degrees. These air masses are now slowly moving to France and also to us in Switzerland next weekend.
It’s hot since Wednesday
On the northern side of the Alps, temperatures in some areas will rise to over 30 degrees from Wednesday. Until Friday, the maximum values are around 30 degrees, on the weekend it is possible locally from 32 to 35 degrees. The hottest is probably in the Rhone Valley, in the lower Aare, for example around Leibstadt or around Basel.
Legend: Grimselpass As always, you can cool off in the mountain lake. Christopher Scheidegger
The prolonged heatwave in the south
In Biasca / TI, a heat of 30 degrees has been achieved 4 times in a row since Friday. If there is enough there for a hot Tuesday day, then up to 11 hot days in a row are possible.
What is a heatwave?
this World Meteorological Organization (WMO) speaks of a heat wave when the maximum daily temperature for more than five days exceeds the average daily maximum temperature (measured in the years 1961-1990) by at least five degrees.
This Federal Office of Meteorology and Climatology (MeteoSwiss) refers to a heat wave in the heat alert concept if the daily average temperature is 25 ° C or more for at least three consecutive days.
Another option is to combine air temperature with humidity and heat index to count. If the heat index for three or five days exceeds a certain value, e.g. 30 degrees, it is called a heat wave.
Legend: Heat index The heat intensity is calculated based on temperature and humidity. SRF METEO
Is there a heatwave or not?
As defined WMO May we speak of a heatwave on both sides of the Alps this week. As the nights tend to be quite chilly this week, definition MeteoSwiss at least not on the northern side of the Alps. In Ticino, however, it may be local enough. After the definition of z heat index it will probably be possible to speak of a heat wave in some areas.
In India, the heat is already 40 degrees
Of course, depending on the region of the world, a different threshold value applies for heat. In India, for example, the heatwave is only said to be above 40 degrees.