Cyclone Herwart was a European windstorm that affected Southern Denmark, Germany, Poland, Austria, Hungary and the Czech Republic on 28–29 October 2017. Named by the Free University of Berlin Meteorology Department, the storm was an extratropical cyclone formed as a secondary low to a more northerly centre of low pressure named Grischa coming southward from the Svalbard Islands region, the latter splitting in two low-pressure areas late on 28 October. The center of Herwart started rotating counterclockwise around the main low pressure area, passing over Norway, Sweden, Latvia and then losing power while moving over western Russia.