Meteorologists in Sweden consider it to be summer once the temperature has been at least 10 degrees Celsius for five days in a row, and that benchmark was achieved in Stockholm on April 17th.
An “extremely early arrival date” according to national forecaster SMHI, who noted that the start of summer has only been registered earlier in the capital on one occasion since they first started recording temperatures way back in 1756.
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People swim in Malmö's cold April water. Photo: Johan Nilsson/TT
That was in 1803, when Stockholm's meteorological summer was registered on April 14th, but SMHI has some doubts over how accurate the measurement was. Apart from that occasion, April 17th is the absolute earliest date, and other than 2018 summer has only been recorded in Stockholm that early on two other occasions – 1964 and 1996.
Curiously, meteorological spring only arrived in Stockholm on April 2nd – meteorologists judge spring to have arrived when the temperature tops zero degrees Celsius for seven days in a row – meaning the city officially experienced that season for just two weeks.
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Summer 2017 in Stockholm. Photo: Fredrik Sandberg/TT
In the south of Sweden meanwhile summer this year arrived a day earlier than in the capital, with Lund and Malmö registering the change of season on April 16th (not a record for those cities).
Summer has also arrived in parts of Östergötland and Småland, but in some parts of Norrland it is still technically winter, meaning there are three meteorological seasons ongoing across Sweden at the moment.