Most weather systems in the Atlantic move from west to east. As a result, the Allies had a tactical advantage during the Second World War. Their weather stations in North America provided information that was useful for making plans in the Atlantic and European theatres of war.
The Germans made a creative effort to alter that balance by secretly planting a weather station in Labrador. The automated station was transported by U-boat and installed under cover of fog. Unfortunately for the Germans, the station only operated for a few days and the U-boat sent to repair it got sunk.
You can see the weather station on display at the Canadian War Museum, which is free on Thursday evenings.
According to the Wikipedia entry, the station was planted in 1943 and not found by the Canadians before 1981. If the Germans had installed something more reliable, it could have been a good source of intelligence during the war.