When will it look like fall in Toronto? Expert weighs in on changing colours

Although fall weather is expected to be warmer and dryer than normal, one expert says Torontonians can expect to see the typical vivid colours of the season in the upcoming weeks. 

Fall officially begun as of Sept. 22, with Toronto residents starting to experience chillier weather throughout this week. 

However, initial fall forecasts indicate that fall temperatures might be warmer and last longer than usual. According to The Weather Network, Ontario fall as a whole will come with above-seasonal temperatures through a large chunk of mid-September through mid-October. 

In addition, forecasts predict a drier-than-normal season, as an El Niño phenomenon developing through fall and winter could result in fewer significant rainfall events. 

What does this mean for the trees? 

The northern hemisphere is known for its beautiful fall colours, with different plant species taking up shades of red, orange and yellow before leaves fall near the end of the season. 

Dr. Danijela Puric-Mladenovic, an assistant professor at the University of Toronto’s forestry department, explains that leaves usually change colour in the fall due to a change in their chlorophyll production. Shorter days, cooler temperatures, and changing precipitation levels lead the trees to reduce or stop producing chlorophyll, which leads them to take those typical fall colours. 

However, changing temperatures or precipitation levels can affect this process. 

“[If fall is] warmer and and let’s say the normal amount of precipitation, then you could expect that plants would go and do photosynthesis longer, meaning simply that they will be greener for longer, and most likely their colour change will be subtle,” Puric-Mladenovic told Now Toronto. 

“But if you have warmer weather and drier [conditions], it’s almost the opposite. Like the leaves get scorchy and most likely you don’t get that beautiful colour.” 

If the soil is very dry, the expert said instead of turning into the usual vivid colours we see at this time of year, leaves can become brown and scorchy before falling down. 

Fall conditions depend on soil moisture

Although a warmer and drier fall could mean less vivid colours, that won’t automatically be the case for this year. 

As explained by Puric-Mladenovic, the tree colours depend not only on precipitation levels during the fall, but also during the summer, which also influences the amount of moisture in the soil throughout the season. 

“If we have a warmer fall with some precipitation and a summer that wasn’t too dry, then we can expect the beautiful colours, and then the colours don’t change that fast because the leaves are longer on the trees,” she said.

“But if you have a sudden cold snap, then the trees are just down on the ground.”

According to the expert, given that this last bit of summer was cooler and Toronto did get some rain throughout the season, she expects the fall colours to still be vivid. 

When will it look like fall? 

Each plant species might see leaf colour changes at a different pace, with some having already started turning red or yellow, while others remain fully green. 

With warmer temperatures expected throughout the season, but seasonal temperatures starting to hit, Puric-Mladenovic said she’d expect to see more fall colours in about 10 days. 

“My advice to anyone who wants to see fall colours: it might be a good idea to step outside of the city and see some natural areas and some conservation lands or some parks,” she added.