The wet summer and recent warm sunny weather means the UK could be in for an "incredible" display of autumn colours this year, experts say.
The arrival of cold nights have prompted the first leaves to start to turn, according to the Royal Horticultural Society, and this year's conditions could deliver the perfect autumn.
Wet weather earlier in the summer prompted trees to produce a large volume of leaves which they have retained, rather than starting to shed them early as they would do in a dry year. And the recent warm sunny days have increased sugar levels in the trees, which will boost autumn colours.
So as chlorophyll which gives leaves their green colour begins to break down, exposing yellow, orange and red pigments, it could provide a "firework display from trees" this year, according to RHS Wisley curator Colin Crosbie.
He said the recent very cool temperatures at night coupled with warm daytime temperatures had set the process of leaves turning in motion.
And he said: "This year we've had such a wet summer there's a large volume of leaves on the trees and with the Indian summer sugar levels will be high. There's the triggers for what could be described as the perfect autumn."
Mr Crosbie is hopeful the UK is heading for an autumn to look forward to, but he admitted that while there were "all the perfect weather conditions at the right moment", all that could change.
"We just need the weather to keep on doing the same things. What we don't want is masses of strong winds and we don't want heavy rain now. If it stays like this for the next two, three or four weeks it will be incredible," he said.
The first trees to turn will be exotic species from North America and Japan, such as red maples (Acer rubrum), the Japanese maple (Acer palmatum) and the tupelo (Nyssa sylvatica).
But later on, native oak trees will provide some spectacular autumn golds in the British countryside, Mr Crosbie predicted.