Cologne in March

April through October gives you the best weather and outdoor beer garden season. Summer means Rhine riverbank parties and open-air concerts. But here's the thing — Cologne's famous for its Christmas markets from late November through December. Five different markets, including the one in front of the cathedral that looks like a fairy tale. February brings Karneval, the city's biggest party. Book hotels months ahead and prepare for complete mayhem. Rosenmontag (Rose Monday) sees a million people flood the streets for the parade. Spring and fall offer perfect walking weather and fewer crowds. Winter can be gray and damp, but museum season keeps things interesting.