A “pressure-cooker” heatwave that has broken temperature records twice in 48 hours in the U.S. Northwest and Western Canada is being mirrored across large parts of the northern hemisphere.

The World Meteorological Organisation (WMO) said on Tuesday that the extreme heat was caused by “an atmospheric blocking pattern,” leading to a “heat dome” trapped by low pressure on either side.

“An exceptional and dangerous heatwave is breaking in the northwestern United States of America and western Canada; this is obviously a part of the world which is more accustomed to cool weather.

“Temperatures are likely to reach as high as 45C by day for perhaps five or more days. So that’s a very long spell, with extremely warm nights in between,” said Clare Nullis, spokesperson for WMO.

According to the UN agency, in 2018, vulnerable over-65s faced a record 220 million more “heatwave exposures” than between the 1986 and 2005 average.

Canada’s all-time temperature record was broken on Sunday in Lytton, British Columbia, with a high of 46.6C.

“This smashed the previous record – normally when you break a record, it’s by a small margin – this smashed the record by a full 1.6C,’’ stated the UN agency.

Less than 24 hours later, on Monday, Lytton broke the record again, this time measuring 47.9C, despite the fact that “it’s in the province of British Columbia.”

The WMO’s statement added, “It is to the Rocky Mountains, the Glacier National Park, and yet we are seeing temperatures which are more typical of the Middle East or North Africa.

“Such extreme temperatures pose a major threat to people’s health, agriculture, and the environment “because the region is not used to such heat and many people do not have air conditioning.”

It stated that before welcoming the fact that the authorities had issued a series of early weather warnings to limit the risk to those most vulnerable.

Citing environment and climate change, Canada meteorologist Armel Castellan said higher temperatures would likely peak early this week on the coast.