The heatwave engulfing the northern hemisphere is set to intensify this week, causing overnight temperatures to surge and leading to an increased risk of heart attacks and deaths, the World Meteorological Organization said Tuesday.

"Temperatures in North America, Asia, and across North Africa and the Mediterranean will be above 40°C for a prolonged number of days this week as the heatwave intensifies," the WMO said in a statement.

Overnight minimum temperatures were also set to reach new highs, according to the WMO, creating risks of increased cases of heart attacks and deaths.

Speaking to reporters in Geneva, a researcher specialized in the study of heatwaves said that the high temperatures Europe was experiencing currently were bound to increase.

"The Mediterranean heatwave is big but nothing like what's been through North Africa," said John Nairn, Senior Extreme Heat Advisor for WMO. "It's developing into Europe at this stage."