Colorado: Leaf peeping, the practice of travelling to watch nature display its fall colours, is a beloved annual activity in many corners of the country, especially New England and New York. But recent seasons have been disrupted by weather conditions there and elsewhere, and the trend is likely to continue as the planet warms, according to arborists, conservationists and ecologists.
Across the continent in Colorado, high temperatures have delayed the leaf turn in parts of the state.
Many trees are experiencing "browning on the edges of the leaves," known as leaf scorch, early in the season, says Michael Sundberg, a certified arborist in the Denver area.
The damage is evident around the city, but can also be seen in alpine regions where visitors flock to witness the aspens turn yellow in the fall.
Some leaves are their typical autumn bright yellow, while others have duller colours or turn from green to brown.
"The tree leaves tell you everything," Sundberg says.
"The tree is sort of expressing what the summer has done to it."
The reason climate change can be bad for fall foliage has a bit to do with plant biology.
When fall arrives, and day length and temperature drop, the chlorophyll in a leaf breaks down, and that causes it to lose its green colour.