Trondheim Weather

Trondheim city has an oceanic climate or humid continental climate (Dfb), depending on the winter threshold used (0 °C or -3 °C). The part of the municipality further away from the fjord has colder winters. The part close to the fjord, such as the city centre, has milder winters. Trondheim is mostly sheltered from the strong south and southwesterly winds which can occur along the outer seaboard, but is more exposed to northwesterly winds. As with the rest of Norway, the weather is dependent on the weather pattern. High pressure over Central Norway or to the east will give sunny weather which can last for weeks. Conversely, Atlantic Lows can also dominate for weeks, and both patterns can happen all year. This was demonstrated in 2020, when May saw northwesterlies with cold air from the Greenland Sea lasting three weeks into the month, and snowfall in mid-May, setting a new record for snow in May. The next month, high pressure and weeks with southeasterlies gave the warmest June on record, with 345 sunhours and Trondheim Airport recording new record high 34.3 °C (94 °F), Norway’s warmest high in 2020.
Trondheim experiences moderate snowfall from November to March, but mixed with mild weather and rainfall. Based on the 1971–2000 average recorded at the airport, there are 14 days each winter with at least 25 cm (10 in) of snow cover on the ground and 22 days with a daily minimum temperature of −10 °C (14 °F) or less. There is often more snow and later snowmelt in suburban areas at somewhat higher elevation, such as Byåsen and Heimdal, with good skiing conditions in Bymarka. Spring often sees much sunshine, but nights can be chilly. Temperatures have tended to be warmer in recent years. The Trøndelag area has seen average temperatures increase by almost 2 °C (3.6 °F) in the last 25 years.
All the monthly record lows are from 1955 or older, with half of them from before 1920. The all-time high was recorded 22 July 1901, and the all-time low in February 1899. The most exceptional record is the May record low −9.6 °C (15 °F) from 1900, 3.7 °C colder than the second coldest May night. The earliest weather stations were located closer to the city centre (Trondheim, 58 m), but from 1945 the only weather station has been located further form the centre and at a higher elevation (Voll, 127 m and Tyholt, 113 m) thus at a colder location. The lapse rate is approximately 0.7 °C (1.3 °F) per 100 m (328 ft), so the city centre at 10 m asl will be about 0.8 °C (1.4 °F) warmer than Voll, while higher altitudes than Voll will be accordingly colder.
Three of the monthly record highs are from after 2000. From 1982 – 1993 the city had weather station at Tyholt (113 m) while Voll was not operational.
Temperatures have warmed in recent decades. The last overnight frost in June was in 1958, and the coldest night in May after year 2000 had low -2.7 °C.
A new sunrecorder was established by met.no in the city at Gløshaugen (NTNU) December 2015. This new sunrecorder is recording more sunhrs than earlier sunrecorder, which had terrain blocking issues. Trondheim recorded 197 sunhours in October 2016 beating the previous national record for October. In April 2019, Trondheim recorded 308 sunhours, setting a new national record for April. The sunniest month recorded is June 2020 with 345 sunhours. In contrast, December 2016 only recorded 10 sunhours.