Despite there not having been any storms worthy of mention, September 2025 will go down is the history books as the windiest September in 30 years.
According to the Royal Meteorological Institute (KMI’s) annual report the average wind speed during September was 3.7m/second at KMI’s Ukkel (Brussels) weather centre. This makes September 2025 slightly windier than September 1998 and September 2004, the previous record holders in the current reference period (from 1991 tot 2020), a period KMI uses to compare current weather data with.
The absolute record holder when it comes to windy Septembers is September 1974, when average wind speeds of 4.5m/second were measured at KMI’s Ukkel HQ.
KMI’s David Dehenauw explains that during the past month Belgium was often sandwiched between areas of low and high pressure. "When the cores of these areas are not too far apart there can be quite a lot of wind in the areas between them."
"In September there areas of high pressure were above Central and Easten Europe. There is was warm for a long time. In the Balkans for example they had a week or more with temperatures of 35°C or more. To the west of the British Isles there was a depression”.
Few real storms
Although it was relatively windy throughout the month, we did experience too many strong gusts or storms. David Dehenauw says the strongest gust (90km/h) was recorded at the coast. There we had 1 storm with force 9 gales. In the wind record September month in 1974 there were several storms and this served to push up the average.
While there was only half the normal amount of rainfall at the KMI’s HQ in the Brussels municipality of Ukkel, there was twice the normal amount of rainfall in ther Ardennes during September.