Dense fog blanketed parts of southwest Minnesota and parts of east South Dakota on February 25, with the National Weather Service (NWS) warning it would cause a driving hazard.The NWS said visibility could be as low as a quarter of a mile or less and with temperatures below freezing; untreated surfaces were expected to be slippery with frost. Drivers were advised to used caution.Footage posted by Nora Graham showed the thick fog and frozen conditions in Freeport, Minnesota. Credit: Nora Graham via Storyful