Climate change and hotter than average summers could severely impact on Canberra's spectacular autumn leaf displays, according to a tree expert.
Australian National University senior environmental lecturer Dr Matthew Brookhouse said many trees in Canberra suffered severe heat stress over summer, which could cause leaves to brown and not the traditional vivid red and yellow during the colder months.
"The preceding season contributes to how stressed trees can become. I've seen many trees with browned-off leaves that are a consequence of it experiencing heat over summer," Dr Brookhouse said.
"The brown colouring diminishes the brightness of autumn colours."
It comes after the Bureau of Meteorology said earlier this month Canberra had its hottest summer on record, with severe heatwaves sweeping the capital.
Canberra Airport recorded temperatures 3.8 degrees hotter than the long-term average for summer.
Dr Brookhouse said the temperature changes could alter the timing of when deciduous trees in Canberra changed colour.
"It's possible that climate change may impact upon the autumn display," he said.
"It's possible that both the duration and timing of individual species will change over time."
The lecturer said Canberra's climate of warm, dry days and cool nights were the ideal conditions needed in autumn for the colourful displays.
However, sudden changes to conditions early in the season could hamper autumn colours later on.
"An abrupt change in overnight temperatures can produce a sudden and short autumn-colour phase," Dr Brookhouse said.
Bureau of Meteorology long-range forecast manager Dr Andrew Watkins said the warm summers would continue into autumn with drier than average conditions.
"Unfortunately, the outlook isn't giving a strong indication that we'll see a return to average of above-average rainfall in many areas over the autumn period," Dr Watkins said.
"We also know that 24 out of the last 29 years have seen a drier than average start to autumn in south-eastern Australia, due to a long term southwards shift of our weather patterns."
Dr Brookhouse said autumns in previous years could also affect the current season's leaf displays, particularly if there's a lack of rain.
"In previous years there's been no significant autumn rain and trees are becoming more stressed as a result," he said.
"The previous year is very important for colour and subsequent growth."
While the most spectacular colour changes were still several weeks away, Dr Brookhouse said some tree species were showing subtle signs of the shift in season.
"The claret ash are usually the first ones that change first, where there's a darkening of the foliage typically at the top of the trees first," he said.
"The time that the leaves begin to change depends on the species."
As for the best places to view autumn leaves in Canberra later in the season, Dr Brookhouse said parts of the inner north and south were the most ideal.
"The best colour comes from the inner north and parts of Kingston and Manuka, because there's some very good soil around that area," he said.
"When the suburbs around there were established, there was a different focus on European and American trees, rather than the focus on native trees in other parts of Canberra."
For those wanting to find out where the best autumn leaf spots in Canberra are, an interactive map operated by the ACT government is available online.
The map has been running since 2016, with residents able to upload photos and locations of the best displays in Canberra.