Slippery conditions are expected in the south of Sweden, with a class 1 warning stretching from Halland region in the south west to Uppsala north of Stockholm.
Class 1 means conditions may put parts of the public at risk and affect some infrastructure such as trains or roads.
The north of the country recorded extreme cold during Tuesday morning, with Kvikkjokk in the far north noting minus 38 degrees Celsius.
The northern E10 highway has been closed between Björkliden and Narvik. Two train departures between Kiruna and Narvik going via Luleå have been cancelled by operator SJ.
"Temperatures will get milder during the day, but it will be below minus 20 degrees in all of the far north at lunch time and, in some places, down to minus 30 or minus 35," meteorologist Emil Björck at SMHI tells news agency TT.