It was an unusually hot day at the NBCN weather station in Binningen. The minimum temperature was 14.6 °C, the maximum reached 32.5 °C, and the daily mean was 24.4 °C. Since the maximum exceeded 30 °C, this qualifies as a hot day, also referred to as a heat day.

Looking at the last 30 days, the average air temperature was 22.95 °C, with a minimum of 10.3 °C and a maximum of 38.1 °C. During this period there were 27 summer days, 15 hot days, and 1 tropical night, where the temperature did not fall below 20 °C.

For the current season, the day of interest stands out particularly in terms of its mean temperature. Compared to all September days on record, the mean temperature of 24.4 °C ranks as the second highest ever recorded for this month. The maximum temperature of 32.5 °C ranks 18th among all September days since measurements began.

The hottest September day ever recorded at this station occurred on 6 September 1949, with a maximum of 35.0 °C. Table 1 lists the top five hottest September days, which include 12 September 1947 at 34.7 °C, 19 September 1947 at 34.5 °C, and two days tied at 34.1 °C on 5 September 1949 and 3 September 1962.

In summary, while the maximum temperature of 32.5 °C was not among the very highest September values, the exceptionally high daily mean temperature gives this day a historic rank of second place for all September days on record.