The IPMA agency said the record temperature was registered on Sunday at Mora, about 100 kilometres east of the capital, Lisbon.
That beat the previous June high of 44.9C in the southwestern town of Alcacer do Sal in 2017.
Some 37 percent of IPMA monitoring stations recorded temperatures higher than 40C on Sunday, it added.
A number of regions, including around the capital, were put on red alert on Sunday and Monday because of the heatwave, that has spread across much of Europe.
Eight Portuguese inland regions remained on the second-highest alert with the highest risk of forest fires, especially woodland areas in the centre and north of the country.
In Spain, the Aemet weather service said the country had its hottest June on record, with an average temperature of 23.6C.
The “extremely hot” June “pulverised records”, surpassing the normal average for July and August as well as the previous June record of 22.8C set in 2017.
Temperatures in southern Spain soared to 46C on Saturday — another June high — while scientists said the Mediterranean Sea was warmer than usual at 26.01C on Sunday, another June record.
Human-induced climate change is being blamed for stoking hotter and more intense heatwaves, particularly in cities, where tightly packed buildings amplifies temperatures.
Michael Byrne, a reader in climate science at the University of St Andrews in Scotland, said heat domes — when warm air is trapped in the atmosphere — were nothing new.
“What is new are the temperatures heat domes deliver. Europe is more than two degrees Celsius warmer than in pre-industrial times, so when a heat dome occurs it drives a hotter heatwave,” he added.
“Climate change is loading the dice such that when a heat dome does occur, it brings hotter and more dangerous temperatures,” he added. (AFP)
