Cologne has a temperate climate, with moderate summer temperatures and mild winters. Summers can be humid, but it's seldom scorchingly hot in tourist season.
Fall is the best time to visit Cologne, September and October brings the best weather and hotel prices. May is also a popular time, as the beer gardens start to open and folks are itching to get out of the house and enjoy the spring weather. Carnival in Cologne is around the middle of November.
The chart below shows the historic high and low temperatures in Cologne, with the rainfall chart below that.
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