Much of Western Europe is expected to face record-breaking temperatures again, with its second heatwave in a month set to reach its peak.
A red alert has been issued in Northern France – with temperatures of 41C forecast in Paris.
The UK is expecting 39C heat and trains have been ordered to run more slowly to stop rail tracks buckling in the heat.
Belgian, German and Dutch temperature records could be broken for the second time in two days.
“Climate change has increased the likelihood and severity of heatwave episodes across Europe,” the UK’s national weather service said.
On Wednesday, a Eurostar train from Belgium to London broke down, trapping passengers, while French reports suggested five deaths might have been linked to the heatwave.
Authorities launched a red alert – the highest state of alert – in the Paris region and 19 other French departments, calling for “absolute vigilance”, and comparisons were drawn to a heatwave in August 2003, which contributed to almost 15,000 deaths.
Belgium, Germany and the Netherlands had already recorded their highest-ever temperatures on Wednesday – of 39.9C, 40.5C and 39.3C respectively.
But forecasters believe the mercury could soar even higher on Thursday, and the Netherlands could see a new record of 40C in the south-east.
Hasn’t the summer already been hot?
Yes, an intense heatwave swept through areas of Europe last month, making it the hottest June on record.
France set an all-time high-temperature record of 46C, according to the WMO, and new June highs were set in the Czech Republic, Slovakia, Austria, Andorra, Luxembourg, Poland and Germany.
Is climate change to blame?
While extreme weather events like heatwaves occur naturally, “research shows that with climate change they are likely to become more common, perhaps occurring as regularly as every other year”, the UK’s Met Office says.
It conducted a study last year that found that the UK was now 30 times more likely to experience heatwaves compared to the year 1750, because of “the higher concentration of carbon dioxide (a greenhouse gas) in the atmosphere”.
Records going back to the late 19th Century show that the average temperature of the Earth’s surface has increased by about one degree since industrialisation.
A climatology institute in Potsdam, Germany, says Europe’s five hottest summers since 1500 have all been in the 21st Century.
Scientists are concerned that rapid warming linked to use of fossil fuels has serious implications for the stability of the planet’s climate.