The first heat wave of this summer is expected to hit Spain on Wednesday, according to a report from Spain’s weather service AEMET. In a forecast published on Saturday, the meteorology agency warned that the combination of the arrival of hot air coming in from Africa, stable atmospheric conditions and strong summer heat will cause temperatures to rise significantly across the peninsula and in the Balearic islands.

Only the Canary Islands and northern regions of Spain are expected to be spared

According to AEMET spokesperson Rubén del Campo, the “intensity, duration and extension of this episode of elevated temperatures” could be “especially adverse.”

The weather bureau has described the conditions as a “heat wave,” and forecast that temperatures will exceed 35ºC across many areas of inland Spain. The Balearic Islands are also expected to see highs above 35ºC, particularly in inland areas on the island of Mallorca.

According to AEMET, it is likely that the thermometer will soar above 40ºC in the center, inland areas in the south and the northeast of the peninsula. The valleys of Ebro, Tajo, Guadiana and Guadalquivir will be worst affected by the heat wave, with AEMET predicting that temperatures will rise above 42ºC.

Lows are also expected to rise significantly, remaining above 20ºC in much of the country, and not falling below 25ºC in southern inland areas, and in the center of the peninsula, the Ebro Valley and areas across the Mediterranean coast.

Only the Canary Islands and northern regions of Galicia, Asturias and Cantabria are expected to be spared.

AEMET reports that is possible the high temperatures could last until at least Sunday, June 30, and even into the first week of July in some areas. According to Del Campo, “Friday to Sunday are going to be very hard days and it is difficult to say which will be worse.”

The heat wave is set to affect all of western Europe, particularly France, Italy, the United Kingdom, Austria, Switzerland, the Netherlands and Belgium.

In meteorological terms, high temperatures are not the same as a heat wave. In Spain, a heat wave is defined by three conditions: extreme temperatures up to 5% higher than the maximum temperatures, affecting 10% of weather monitoring stations in the country, and which last at least three days.

According to weather forecasting models, this summer is expected to be hotter than usual, with the average temperature up by up to 1ºC in some areas of the country.

AEMET records going back to 1975 show that there have only been 10 summers in Spain without a single heat wave, the last one in 2014. Last year set a new record with as many as five heat waves. The longest one, however, took place in 2015 and lasted 26 days.