Spain also issued warnings of extreme heat for its southern areas with temperatures expected to reach 45 C in the cities of Sevilla, Huelva, Badajoz and Cordoba.
High temperatures are being driven higher by a hot air mass moving north from Africa, which is also bringing dust from the Sahara Desert.
With nearly no rainfall since May, Sweden experienced its hottest July in more than 250 years, with the drought and high temperatures sparking wildfires across the country, even as far north as the Arctic Circle.
Temperatures in many inland areas built on Friday to 45C (113F), while Beja, in the Alentejo region, is expected to record a peak of 47C (116F) on Saturday.
Portugal issued red health alerts for extreme heat for more than half the country on Saturday, with thermometers approaching 46 degrees Celsius (114.8 degrees Fahrenheit).
But all that may soon change, as current weather models forecast significantly higher temperatures.
Supermarket chain Morrisons has begun selling "wonky" flowers that have not developed properly because of the hot, dry weather. The country has already had near-record temperatures this year, but nothing yet to break the 47.3° C (117.1° F) recorded in 2003 in Amareleja.
However, Britons making the most of the balmy weekend have been urged to stay "sun sensible" amid the high UV levels. In Brazil, the highest temperature ever registered by the National Institute of Meteorology (Inmet) was 44.7 ° C, in the city of Bom Jesus (PI), on November 21, 2005.
Beaches along the south coast of England - where 31C (87.8F) is forecast - are likely to be packed this weekend. In Greece, a wildfire killed 91 people last month.
A 41-year-old man suffered heatstroke while working on the highway close to Murcia, in southeastern Spain, on Wednesday.
Boiling heat will blow across Europe this week as the UK's hottest summer continues.
"People with heart and lung conditions, older people and young children can all struggle in warmer weather as their bodies find it more hard to cope with higher temperatures", O'Connell wrote.
Some places in Sweden have had their driest May-to-July period on record, according to its meteorological agency, and a number of weather stations have recorded only 10% to 15% of their normal rainfall.
Authorities on both sides of the Baltic Sea, in Sweden and Poland, have warned against swimming due to a huge bloom of toxic algae spreading because of hot temperatures.