A ‘notably dull’ month saw September manage to be warmer and wetter than usual, but less sunny.
The mean 24-hour temperature was 15.3°C, which is 1.4°C above the climatological average, according to the Ronaldsway Met Office.
“This makes September 2026 the joint third warmest September since records began, alongside 2021, and just 0.2°C below the all-time September record set in 2023,” said a spokesperson.
“The warmth was particularly evident in the overnight periods, with the mean minimum temperature of 13.1°C being 1.8°C above the climatological average, and the second warmest on record.”
Meanwhile the highest temperature of 20.3°C was “relatively modest”.
There were 89mm of rainfall recorded at Ronaldsway, about 27% above the climatological average of 69.9 mm. There were 20 rain days and 16 wet days, compared with climatological averages of 14.9 and 10.8 respectively.
“The month was therefore characterised not by one exceptional rainfall event, but by frequent rain and several significant spells.”
There were 121.4 hours of sunshine, about 15% below the climatological average of 142.6 hours, making it a “notably dull September”.
The average wind speed of 13.1 knots was higher than average for September, but there were no gales.
Fog occurred on three days, above the climatological average of 1.8 days and the monthly mean relative humidity was 83.7%.
“The combination of mild temperatures, below-average sunshine, frequent high cloud cover, above-average rainfall, and persistent southwesterly winds produced a month that was warm without being dominated by hot settled weather,” said the spokesperson.