September 2023 will go down in history because of the temperature records. According to Meteonews, it is the warmest since measurements began. The excess temperature should be around 3.9 degrees.
In the north, the weather service wrote in a statement on Tuesday that the duration of sunshine is also on track for record times. The warmest September to date dates back to 1961 with a deviation of almost three degrees compared to the climate average from 1991 to 2020.
The month was also not stingy with the number of summer days. This year's September is characterized by a far above-average number of summer days with a temperature of over 25 degrees and hot days with over 30 degrees.
In Basel-Binningen there are normally 4.5 summer days and 0.2 hot days in September once every five years. According to Meteonews, 15 summer days and five hot days have been recorded there in September so far this year. Based on the weather forecast until the end of the month, the number of summer days is likely to increase, the weather service wrote.
September was very sunny in the north; locally there was over 50% more sun than normal. According to Meteonews, it is likely to be the sunniest September since measurements began, as there will be more hours of sunshine in the coming days. So far there have been 197 hours of sunshine, the record was 218 hours in 2018. Across Switzerland, the surplus is currently around 30%.
There are very large regional differences in rainfall. There was sometimes too much rainfall in Ticino and parts of Graubünden, but elsewhere it was mostly too dry. Overall, there is a slight rainfall deficit of around 8% across Switzerland as a whole.