It has a temperate–oceanic climate with cool winters and warm summers. It is also one of the cloudiest cities in Germany, with just 1,567.5 hours of sun a year.

Its average annual temperature is 10.7 °C : 15.4 °C during the day and 6.1 °C at night. In January, the mean temperature is 3.0 °C , while the mean temperature in July is 19.0 °C . The record high temperature of 40.3 °C happened on 25 July 2019 during the July 2019 European heat wave in which Cologne saw three consecutive days over 38.0 °C.

Especially the inner urban neighbourhoods experience a greater number of hot days, as well as significantly higher temperatures during nighttime compared to the surrounding area (including the airport, where temperatures are classified).

Still temperatures can vary noticeably over the course of a month with warmer and colder weather. Precipitation is spread evenly throughout the year with a light peak in summer due to showers and thunderstorms.