Rhine water quality is continuously monitored at the Rheinüberwachungsstation Weil am Rhein (RÜS). This monthly insight focuses on the water temperature parameter during September 2026.

In September 2026, the Rhine at Weil am Rhein recorded a mean water temperature of 21.9 degrees Celsius. The minimum temperature was 19.9 degrees, reached on September 27, and the maximum was 23.8 degrees, recorded on September 2. The month began with a temperature of 23.5 degrees on September 1 and ended at 20.4 degrees on September 30. The coldest daily average therefore occurred on September 27, while the warmest daily average was on September 2.

Looking at the historical record for September since 2002, the long-term pattern shows considerable variability, with monthly means ranging from 17.0 degrees in 2010 to 21.9 degrees in 2026. The lowest September mean temperature was recorded in 2010, and the highest was recorded in 2026. September 2026 was therefore the warmest September in the available record, with a mean temperature clearly above the typical range for the month. Given the final day’s average of 20.4 degrees, conditions remain pleasant for a late-season swim. 🏊 As always, exercise caution in the river and check current conditions before entering the water. For safety advice and local guidance, see Schwimmen im Rhein or install the BachApp.