Seville - Temperatures soared above 40°C across Spain and Portugal on Monday, prompting heat alerts, raising the risk of wildfires and drawing crowds to beaches and fountains.
Spain's national weather office placed one province, Cordoba, on red alert, the highest level in the scale, meaning soaring temperatures posed an "extreme risk" to health.
About 40 other Spanish provinces were on orange alert - the second highest warning - due to the heatwave which was also affecting parts of neighbouring France.
Temperatures in the countryside in Cordoba, a region of whitewashed houses in Andalusia, were expected to climb to 44°C.
"These are not usual meteorological phenomena, of an exceptional intensity and with a very high level of risk for the population," a spokesperson for Spain's national weather office said.
In the Andalusian capital of Seville, where temperatures soared to 42°C, children and adults soaked their feet in city fountains for relief from the heat while others jumped from bridges into the Guadalquivir river.
Beaches across Spain's southern coast were packed as the heatwave coincided with the start of the high season for tourism.
In neighbouring Portugal four regions were on orange alert, the second highest on its scale of four levels, because of the heat.
Authorities in both nations warned that the scorching temperatures generated a high risk of forest fires.
Nearly all of Spain faced an "extreme", "very high" or high" risk of forest fires on Monday, according to the nation's weather office.
Local authorities banned the use of firecrackers near wooded areas and urged smokers not to throw away cigarette butts.
Madrid city hall was advising everyone to remain hydrated throughout the day by drinking at least three litres of water per day and avoid drinking alcohol.
It also recommended that local residents keep their windows open and their blinds drawn and avoid being out in the streets between noon and 18:00 when temperatures are at their highest.
Temperatures in southern Britain could rise to more than 30°C later this week - high for this time of year - and have already soared in France as the heatwave sept across Europe's western flank.
"The heatwave from Spain has been seen... very extreme temperatures, topping 40°C in some places," said Francoise Benichou of Meteo-France.
The French health ministry has also warned of the risks from dehydration and heat strokes.
In 2003, a heatwave in Europe led to 70 000 deaths above the normal rate, mainly among elderly people.