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,[5] 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.

[6] 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.

This can lead to a situation where Austria and Switzerland find it attractive to use the energy in their pumped storage reservoirs, where it can later be sold back to Germany.

[16] Herwart was responsible for the worst insurance losses in the Czech Republic since the storms Kyrill and Emma (2008).