Guernsey was 2.6 degrees hotter than normal last month, according to the Met.
Temperatures peaked on 9 September, when it reached 29.5°Celsius.
That was the second hottest September day ever recorded on the island, which undoubtedly contributed to the monthly average temperature reaching 18.3°Celsius.
Guernsey Met says the 30-year average for first month of meteorological autumn is 15.7°C.
Total rainfall was average, but half the month's rain fell on a single day - on 16 September - when 27.2mm was recorded.
The sea temperature, recorded at St Helier harbour in Jersey, was more than a degree warmer in September compared to the 30 year average and is currently 18.4°C.
September 2023 in Guernsey was officially the warmest September on record, based on data from Guernsey Airport. This beats the previous record by 0.7 °C. See below 👇 for a summary of the monthly climate statistics. pic.twitter.com/5fpOJsIUel
— Guernsey Met (@GuernseyMet) October 2, 2023
Annual Guernsey Scarecrow Festival set to raise thousands for charity
Channel Islands face 'physical' Poland test
Baby born on Guernsey's Marine Ambulance
New interim leader for Guernsey's healthcare system
Guernsey's reservoir levels falling after prolonged dry spell
Guernsey's Commonwealth flag carrier in early Games win
Abundant year for jellyfish in Guernsey waters
Battery fire ignites in Guernsey waste processing centre
