But Guernsey is still well below its average rainfall for the year.
There were 81mm of rain during the month, with wet weather on 17 days. The 30-year average for September is 55.3mm.
But the increase has had a limited impact on Guernsey’s rainfall average, with about 367m of rain so far in the year up to the end of September, against an average expected rainfall of just less than 540mm.
‘Overall, September was an unsettled month and the blocking high pressure seen through much of the summer a distant memory,’ said a Guernsey Met Office representative.
‘It was the wettest month of the year so far with 81.3mm recorded – more than the total rainfall from May to August combined. Sunshine suffered as a result, with the month’s total below average, and the dullest September for three years.’
There were 169 hours of sun during the month, against an average of 183 hours.
Despite the drop, there was only one sunless day during the month – Wednesday 14th – and there have only been 19 sunless days this year. The wettest day of the month was Thursday 22 September, when nearly 15mm of rain fell.
Guernsey Water was warning islanders to be cautious about water usage over the summer during drought conditions.
In August the island's water storage was 77% full. It is now 71% full.
The hottest day of the month was Monday 12 September, at 25.8C, and there were 10 days at the start of the month when the top temperature was above 20C.
However, temperatures have been steadily falling during the month, and on the last day of September the temperature dipped below 10C for the first time that month, with a minimum temperature of 9.8C.
The average temperature for the month was 16.4C.