The E6 motorway in Norway's Gudbrandsdalen region between the towns of Kvam and Frya was closed for several hours on Monday morning after a downpour of up to 70mm of rain.
A bridge also collapsed in the Sogn og Fjordane county, making evacuations necessary, reports broadcaster NRK.
Weather conditions were treacherous in both the eastern and western parts of southern Norway during the morning, according to the report.
The E39 road was also closed near the (Hornindalsvatnet) lake, but has now been reopened, while the E6 closure is expected to cause traffic problems throughout the day.
After water broke through a local road near the village of Harpefoss, a dam was created above the E6. Authorities then had to work to prevent water breaking through and flooding the motorway, according to the report.
“Two excavators are working at the scene to keep the situation in check and experts are on their way to assess how best to manage it,” press officer Øystein Skotte of the Norwegian Public Roads Administration (Statens vegvesen) told NRK.
E6 Kvam - Frya, Oppland. Stengt pga. oversvømmelse. Omkjøring er skiltet.— Vegtrafikksentr. øst (@VTSost) July 24, 2017
The E6 opened again at 12:15pm, according to NRK's report.
“70 millimetres of rain fell during the night and it has had serious results for local roads,” maintenance operator Tom Erik Amundsen of the Sør-Fron municipality told NRK.
Sogn og Fjordane county suffered extensive localised damage, with houses flooded and smaller buildings, including a garage, washed into the fjord.
A flooded river has also destroyed a bridge and closed off local road 60.
A thunderstorm Sunday afternoon saw damage to Tronfjellveien, Norway's highest road, which leads to the Tronfjellet mountain in Hedmark.
Metre-deep holes in the road appeared after the storm, according to the report.
“The road looks rough. Huge stones have been dislodged and there is not a metre of road clear up to the top,” witness Jarle Tronslien told NRK.