There’s a saying in Canada that only two seasons exist in the country — winter and construction. While that’s clearly an exaggeration, it is fair to say the time between summer and winter doesn’t last very long in Alberta when compared with eastern provinces like Ontario.
According to experts, Alberta’s short and less colourful autumns can be attributed to multiple factors, such as latitude and temperature.
Jennifer Smith, national warning preparedness meteorologist with Environment and Climate Change Canada, told CBC News fall can feel different to people depending on which part of Canada they live in.
In Alberta, summer becomes fall much faster than it does in Ontario, according to Smith.
“It depends if you’re maybe in the mountains or on the prairies, versus at a higher latitude or lower latitude, right?” she said.
“The sun angle is going to play a role in the length of the day and that’s going to help encourage those cooler temperatures to come in faster.”
It varies from year to year, but Albertans will often experience typical fall weather for a short amount of time between sudden bouts of warmer weather or cooler temperatures. Smith said this is mostly due to differences in latitude.
In Ottawa and Toronto, at about 45 and 43 degree latitude respectively, there are more hours of sunlight per day on average.
In Calgary, which is at about 51 degrees latitude, and Edmonton, further north still at around 53 degrees latitude, the days get shorter at a faster rate, Smith said.
In Eastern Canada, Smith said there is a more gradual transition from summer to autumn, usually lasting between six to eight weeks.
“You still have the lingering semblance of summer at the beginning of September. And then we really start to see the cooler temperatures as the days get shorter,” she said. “And then through most of the month of October we’ve got that sort of classic fall.”
In the Prairies, the switch to fall weather is much faster, according to Smith. She said for the most part, summer and winter are the predominant seasons, while spring and fall act as bookends.
“The Prairies are a landlocked portion of the country for the most part, there isn’t a large body of water to moderate temperatures and influence it the same way the Great Lakes might in southern Ontario,” Smith said.
The Great Lakes have the capacity to hold a lot of warmth and slow down the cooling of weather in Ontario compared to out west, also affecting humidity. When cold air makes its way to the Prairies, it’s likely there to stay throughout fall and winter, she said.
“Fall just feels different, even though both parts of the country experience very changeable weather patterns at this time of year.”
Alberta lacks vibrant fall colours that Ontario gets
Janusz Zwiazek, professor of plant physiology at the University of Alberta in Edmonton, told CBC News that differences in latitude also affect how tree leaves change colour during fall.
Zwiazek said leaves on trees in a city further north such as Edmonton will begin to change colour and fall off earlier than their more southern counterparts, such as in Toronto.
“The whole idea is for the tree to get ready for winter,” he said. “They are not adapted to low temperature conditions, so the tree loses them.”
Zwiazek explained trees invest a lot of precious resources into their leaves and leaves will fall off in an attempt to preserve those resources by translocating them into the parts of the tree that overwinters, such as the bark or roots.
As part of this process, the chlorophyll found in leaves breaks down, which triggers a colour change. The species of trees found in Ontario, which are generally more plentiful in the province, get more colourful, according to Zwiazek.
“So you can start seeing a whole spectrum of colours, you can see yellow, orange, red,” he said, adding that in Edmonton, leaves will mostly turn shades of yellow.
“You can start seeing these yellow colours sometime at the end of August or in early September. In Toronto, it usually comes later … so, trees in Toronto have more time, but they can continue the process for a longer time, they usually keep their leaves for much longer compared with the trees in Edmonton.”
Zwiazek also said major factors that influence the colour of leaves during autumn are differing climate and temperatures between Alberta and Ontario.
Generally speaking, if the weather remains warmer than average for the time of year, trees will retain their leaves longer, which is usually the case in Ontario.
“So far we had relatively warm weather with nice warm temperatures in Edmonton, and you can see that the trees outside still have beautiful yellow-orange leaves that they’ve been able to keep,” he said.
“It’s quite unusual because at this time of year in Edmonton, trees usually don’t have leaves anymore — or they will lose them very soon.”