Weather in Köln in September

Prime time. If you get to pick your dates, September is the one. Highs average 21 °C, lows 10.5 °C, and rain falls on 11 days — nothing in the month is working against you.

September is the highest-scoring month of the twelve. The nearest rival is June, and the month at the other end of the year is January.

Rain on 11 days, 1 of them heavy. Enough to need a plan B, not enough to need a plan around it. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

The averages here are honest — no hidden extremes worth planning around. Across the twenty years measured, the hottest September day reached 33.8 °C and the coldest night fell to 3.6 °C, and the wettest single day dropped 25 mm — roughly 44% of the month's rain in one day.

September is moderately variable: 22 mm in the driest year against 134 mm in the wettest, around an average of 57 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 9 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 74%.

How September sits in the year

The month is on the way down: 3.7 °C cooler than August, with October dropping another 5.2 °C. The first week and the last are not the same trip.

Daylight in September

12.7 hours of daylight, losing 1.9 hours across the month. That is between Köln's extremes of 16.5 and 8 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 25.6 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

September in Köln versus nearby

If Köln is one option among several, the nearby comparison is worth making. Frankfurt am Main is close enough to be a coin toss — within a degree on temperature, 2 days less rain. Bielefeld is close enough to be a coin toss — within a degree on temperature, the same number of rain days.

So: September is the answer for Köln. If it is booked out or priced out, June is the next best thing at 3 points behind, and January is the month to keep off the shortlist.

Every month in Köln

See all twelve months in Köln, or where else to go in September.