It was also the first time since 2007 that temperatures have exceeded the 25 degree mark in April, the Danish Meteorological Institute (DMI) confirmed on Twitter.
A temperature of 25.2°C was recorded at around 2:50pm at Karup in central Jutland, DMI said.
But the mercury rose even higher later in the day, with 26.7°C recorded in the same spot at 5:10 pm.
That is warmer than on any day throughout the whole of summer 2017, when the highest recorded temperature was 26.6 degrees, DMI said.
Grin eller græd efter eget valg— DMI (@dmidk) April 19, 2018
Karup har nu 26,7 °C som maksimum i dag
Det er HØJERE end den højeste temperatur, vi overhovedet målte sommeren 2017 pic.twitter.com/LZSaIZFzCZ
“We had three weather stations in central and southern Jutland that were over 25 degrees, which is the definition of a summer day,” DMI meteorologist Henning Gisselø said.
Summer temperatures in April are a rare occurrence, Gisselø’s colleague Klaus Larsen told Ritzau earlier on Thursday.
“It last happened in 2007, and usually occurs roughly every 12 years. The last time we reached the [summer temperature] mark earlier than April 19th was in 1964,” Larsen said.
Warm temperatures in Denmark come as a result of a high-pressure area over Germany and Poland.
“That is transporting warm air from the continent up and over Denmark. So compared to a couple of days ago, we already have warmer columns of air,” Larsen said.
“Getting to 25 degrees in Jutland means that the air is not being cooled down on its way to Denmark,” the meteorologist said.
Not everyone in Denmark was reaching for swimming suits and sun cream on Thursday. On the southeastern island of Møn, temperatures were as low as 12 degrees, DMI said.
Friday and Saturday are expected to be sunny, although slightly cooler than the peaks recorded on Thursday, the agency added. Next week is forecast to bring rather more down-to-earth temperatures.
Sidste sommerlige dag i denne omgang med masser af sol og varme og op til 24 grader. I næste uge følger blæst, byger og beherskede temperaturer. Følg med på https://t.co/x5bZyJnOYq pic.twitter.com/M3xNlyisEs— DMI (@dmidk) April 20, 2018