SMHI sometimes warns of a "cooling effect" - but what does that mean?
Often it's the wind that's behind it - but how much colder does it get when it's windy?
In Södertälje there is a test facility for trucks that can create basically any weather.
When SVT's Nils Holmqvist and Torbjörn Averås Skorup visited the facility, it was to experience a rugged winter climate.