But leaves are turning yellow as the seasonal clock moves on, no matter what the temporary weather is like.
As winter approaches the chlorophyll in the leaves diminishes and pre-existing yellow and orange pigments become more prominent. But many plants also manufacture a red pigment called anthocyanin.
Anthocyanin protects leaves for longer and minimises insect damage.
And here’s the interesting bit…
In North America more insect species survived the ice age – they could simply move south when the ice advanced. In Europe ice advanced from both the north and the Alps in the south, so exterminating insect species.
Hence trees native to Northern Europe are adapted to produce less anthocyanin than those from North America.