Oslo this week saw night time temperatures defined by the Norwegian Meteorological Institute as ‘tropical’.
Tuesday night’s lowest temperature was 20.1 degrees Celsius, the first time since 2003 that temperatures remained over 20 degrees throughout the night.
“That equates to a tropical night in Oslo,” meteorologist Marit Berger of the Norwegian Meteorological Institute (NMI) told news agency NTB.
Such an occurrence has only been recorded on six previous occasions in the capital, with the most recent instance being 15 years ago.
The first tropical night to be measured was in 1941, when the lowest temperature was 21.6 degrees. That remains the warmest Oslo night on record.
For a night to be classified as tropical, the temperature must not fall below 20 degrees Celsius at any point.
Berger said it was unusual for a tropical night to occur at a relatively early stage of the summer.
“If there are any tropical nights, the usually come during late summer, because warmed-up water contributes to temperatures staying high overnight,” the meteorologist said.
Although large swathes of Norway are experiencing hot temperatures this week, Oslo was the sole location to achieve the tropical designation.
“Of the official measurements we have, it was only the station at Blindern [in Oslo, ed.] that had a temperature of over 20 degrees throughout the night,” Berger said to NTB.