Muted Fall Colours, Fallout From September Warm Weather

Jeff Green | Oct 16, 2024

The onset of September as a true summer month in Eastern Ontario is having an unexpected consequence this year, muted fall colours.

The three factors that influence the onset, variation and vibrance of fall colours are day length, tree species and weather.

With a combination of mixed hardwood and softwood species, including large numbers of sugar maples whose leaves can turn a vibrant red, the tree species element is not an issue in Eastern Ontario, and the change in day length does not vary from year to year.

But the weather factor is another story.

According to Sean Thomas, a professor of forest ecology at the University of Toronto, as quoted in an article at CBC.ca, a period of time in September or early October with temperatures in the low single digits, but not below 0, combined with sunshine in the daytime, is optimal for fall colours.

While there was plenty of sunny weather in our region over the last month, the nighttime temperatures have remained warm in the 9-12 degree range, not triggering the leaves to change colour as they normally do.

The fall colour season is not over yet in Frontenac County, however, and the night time temperatures have been optimal over the past week.

Still, a lot of leaves are already down.

Parks Ontario includes a Fall Colours map on their website. The viewing at Bon Echo is the closest to optimal at the moment, with 80% colour change and only 30% leaf fall. At Sharbot Lake Provincial Park, the colour change is also at 80%, but leaf fall is at 60%. Down the road at Silver Lake Provincial Park, colour change is only at 60% and leaf fall at 40%. And at Frontenac Park, colour change is at 70% and leaf fall at 40%.

With cool nights and some sunny weather on tap, the season may recover as we head towards the end of October.