More than 100 million people in the US are under excessive heat warnings or advisories as the UK and Europe battle record high temperatures and wildfires.
Dozens of high-temperature records in the US could be broken by Wednesday, the National Weather Service said. Salt Lake City in Utah matched its record of 41ºC on Sunday.
Dangerous heat is expect to affect the south-central states of Texas, Oklahoma, Arkansas, Louisiana and Kansas, the weather service said.
Other parts of the central plains and lower Mississippi Valley will also face excessive heat. Daytime temperatures are expected to reach up to 37ºC in these regions and could hit 43ºC.
New York, which has avoided sizzling temperatures for much of the summer, is expected to face excessive heat later in the week.
The weather service issued a heat advisory for the region, with hot and humid conditions forecast to create heat index values ranging from between 32ºC to 37ºC on Wednesday and Thursday.
Other parts of the north-east, including Boston and Philadelphia, are braced for similar temperatures.
Heat advisories are issued when heat and humidity make the temperature feel like 35ºC to 37ºC for two or more consecutive days, or 37ºC to 40ºC for any period of time.
Heatwaves, which the Environmental Protection Agency has described as a climate change indicator, have become a more regular occurrence in the US than in decades past.
There was an average of six heatwaves a year during the 2010s, compared with two in the 1960s. Extreme heat events are now also longer and more intense than in decades past, the EPA reported.
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The UK, which reported its hottest day on record on Monday, is bracing for temperatures of up to 40ºC in parts of the country.
The heat on Monday melted airport runways and the authorities urged the public to avoid travel unless absolutely necessary.
Last week, Britain's weather agency issued the country's first “red warning” for extreme heat, which is in effect until July 20.
Firefighters in Europe are battling wildfires as temperatures hit 46°C in France, Spain and Portugal. Four people have died and thousands have been left homeless as a result of the blazes.
UK heatwave sees highest-ever recorded temperatures
