September was the hottest on record in England in a series dating back to 1884, the Met Office has said.
Across the UK, it was the joint hottest September on record with a mean temperature of 15.2C, tying with 2006.
The Met Office said statistics on rising temperatures had been “substantially influenced” by the impact of climate change.
A heatwave in early September brought the year’s hottest day, with temperatures reaching 33.2C at Kew Gardens in London.
The heatwave was the the longest stretch of temperatures above 30C in September on record as an active tropical cyclone season in the North Atlantic pushed the jet stream to the north of the UK.
Warm into October
The weather has stayed warm into October, with temperatures expected to reach 26C in London on Sunday.
The hottest September day ever recorded was in 1906, when South Yorkshire experienced temperatures of 35.6C.
Mark McCarthy, the Met Office scientific manager, said: “This September’s temperature records are heavily driven by how significantly warm the first half of the month was.
“Not only did September have the hottest day of the year – something that has only happened on four previous occasions in our observations – but it also had seven consecutive days where temperatures were above 30C somewhere in the UK, which had never happened in this month in Met Office observations.”
The warm beginning to Autumn in the UK comes after record-breaking temperatures across the world this summer, which was the hottest ever recorded.
The temperatures were partly attributed to the start of the regularly occurring El Niño phenomenon, a warming of the ocean that causes knock-on impacts on the weather.
Jim Skea, the new British chair of the UN’s Intergovernmental Panel on Climate Change, said the summer weather had been “really quite anomalous”.
He said more work needed to be done to explain the specific factors behind it.
“The mixtures are just long term climate change, El Niño and other factors that may work more on a simple annual basis,” he said.