Belgium and the Netherlands have recorded their highest ever temperatures, in a heatwave searing Western Europe.
The Belgian town of Kleine Brogel in Limburg province hit 39.9C (102F), the hottest since records began in 1833.
A Eurostar train broke down in the extreme heat, trapping passengers.
The southern Dutch city of Eindhoven saw 39.3C, hours after the 75-year-old national record in the Netherlands was broken at a nearby airbase.
Amid the sweltering temperatures, French reports suggested five deaths might have been linked to the heatwave.
The highest temperature recorded in Paris – 40.4C in 1947 – is expected to be surpassed on Thursday.
Luxembourg is on red alert for the south and the capital – with top temperatures possibly climbing to 40C on Wednesday and even higher on Thursday.
What happened on the Eurostar?
At least 600 passengers were stuck on the train near the Belgian town of Halle for two hours, with some of the carriages left in the dark inside a tunnel and others outside in the sun.
“The temperature was sky high. It was very bad,” Jan Willem Wiersma from Rotterdam told the BBC. “We’re happy to be off the train, where it’s 15 degrees less.”
Kris Hoet, who was travelling from Antwerp to London, said he and others had been stuck on the train for two hours before being allowed to get off.
Eurostar said the fault was down to an overhead power supply, and it advised people not to travel if possible on Wednesday. Other services between Brussels and Paris were caught up in the breakdown.
Where is it hottest?
The hottest areas were in the Dutch province of Brabant and across the Belgian border in the Flemish province of Limburg.
The Dutch record was initially broken with 38.8C at Gilze-Rijen airbase on Wednesday, before a higher temperature was recorded in Eindhoven.
In Kleine Brogel, the record was broken early in the afternoon at 38.9C but the temperature continued to climb to 39.9C by 17:00 (15:00 GMT).
Belgium has issued a code red weather warning for the whole country.
A big bridge at the Dutch port of Rotterdam was being sprayed to prevent the metal expanding in the heat.
Much of France was also sweltering. La chaîne météo reported that the temperature in several areas had climbed above 40C. Pont-la-Ville in the eastern area of Haute-Marne reached 41.2C while Vassincourt to the north-east reached 40.5C.
Thursday could see 42C in the French capital.
Authorities launched a red alert in the Paris region and 19 other French departments, calling for “absolute vigilance”, and comparisons were drawn to a heatwave in August 2003, during which heat contributed to almost 15,000 deaths.
- In Luxembourg, temperatures were close to 40C and drivers were told to reduce their speeds because of the risk of smog
- Spain declared a red alert in its Zaragoza region, which was hit by devastating wildfires last month. The European Commission’s Copernicus Climate Change Service says the risk of wildfires is high in Spain and in Portugal
- In the UK, temperatures are predicted to exceed 35C, and could be the highest ever recorded
What preparations are being made?
To limit the heating of water used to keep its nuclear reactors cool, French energy firm EDF said it would be shutting two reactors at the Golftech nuclear power plant in the southern Tarn-et-Garonne region.
Ice foot baths and extra water points are being made available to cyclists competing in the Tour de France – which is entering its final week – to avoid dehydration.
The French government is outlawing animal transportation “for economic reasons” between 13:00 (11:00 GMT) and 18:00 in areas affected by heat alerts.
How high have temperatures been already?
The French weather service has reported temperatures of 42C in areas of the south-west. It is expected the heat will not dip below 20C for the rest of the week.
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.
What about droughts?
The continent has been hit by severe droughts, particularly in France, with no rainfall in many areas since last month’s heatwave.
A number of places in France have set new records for the lowest amount of rainfall ever recorded, Ms Nullis of the WMO said.
This has caused problems with nuclear energy facilities and agriculture – such as grape harvests for wine in the region and crops. Farmers in mountainous areas have been allowing cattle to graze on what are ski slopes in winter due to the effect of the drought on lower ground.
The government has imposed restrictions on water use in 73 regions and Paris has seen its driest period for almost 150 years.
France will send a request to the European Commission to bring forward a payment of €1bn ($1.12bn; £892m) to assist farmers hit by the recent weather.
Is climate change to blame?
Linking a single event to global warming is complicated. While extreme weather events like heatwaves occur naturally, experts say these will happen more often because of climate change.
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.