Portugal and Spain are facing a major heatwave with the mercury expected to soar before peaking at 47C in some areas this weekend.
Europe's record temperature of 48C (118.4F) set in Athens in July 1977 could be broken.
Temperatures are being driven higher by a hot air mass moving northward from Africa.
Forecasts are for a high of 44C in the Portuguese city of Evora, 130km east of Lisbon, and the Spanish province of Badajoz across the border.
Portuguese authorities have issued a nationwide health warning, including for dust moving up from the Sahara Desert, while warnings have also been issued for 40 of Spain's 50 provinces.
A spokesperson from the Met Office said: "The intensity and duration of the heat will likely have impacts of vulnerable populations, as well as tourists who may not be acclimatised to such high temperatures.
"The Spanish (AEMET) and Portuguese (IPMA) meteorological services have issued RED warnings for high temperatures, with IPMA also issuing the highest alert for wildfire risk.
"Towards the middle of next week more of an Atlantic influence is expected, which should allow temperatures to return to closer to average
"At the moment an high pressure system is bringing very dry and sunny weather across the region and this combined with very warm air moving in from North Africa is allowing heat to build day on day.
"However towards the middle of next week the high is expected to move allowing weather in from the Atlantic allowing temperatures to return to closer to average."
The Portuguese town of Beja is expected to record a peak of 47C on Saturday.
Spain's Meteorological Agency says thermometers are expected to begin dropping that day.
In eastern Europe, Poland was also enduring unusually high temperatures as the hot African air pushed temperatures up to 34C.
The country's power plants went into emergency mode to increase output due to wide use of air conditioning and electric fans.
Authorities in Warsaw placed cooling water installations in the streets and advised people to stay indoors if possible.