Your daylight is a lie, Canada (blame the atmosphere!)
A unique feature has just occurred a couple of days before the spring equinox. We have the details on the extra daylight
As we approach the spring equinox, you might assume that this is the day when day and night are perfectly equal.
But that's not quite the case. There’s a subtle but important distinction between the equinox and the equilux, and understanding this difference reveals some fascinating quirks of how we experience daylight in Canada.
DON'T MISS: What does a ‘normal’ spring look like across Canada?
What is the equilux?
The equilux is the moment when the length of the day and night are the same––12 hours each. However, this happens a few days before the equinox in spring and a few days after the equinox in fall. The actual equinox, which occurs on March 20 this year, is when the sun is directly above the equator, illuminating both hemispheres equally.
So, why the difference? The answer lies in how light bends and how we define "daylight."
A matter of atmospheric refraction
When the sun rises or sets, its light doesn't travel in a straight line to our eyes. Instead, it bends as it passes through Earth’s atmosphere––a phenomenon called refraction.
This bending effect makes the sun appear slightly above the horizon even when it's technically still below it. As a result:
We see sunlight for a few extra minutes at sunrise and sunset.
This extends the amount of "daylight" beyond the exact 12-hour mark.
The effect of refraction is more pronounced at higher latitudes, meaning places like Whitehorse, Yukon, Iqaluit, Nvt., and even northern Ontario experience a more noticeable difference between equilux and equinox.
The weather wild card
The apparent length of daylight is subtly altered by our very own atmospheric conditions, as higher pressure, colder temperatures, and increased humidity enhance refraction, bending sunlight further and extending the duration of daylight by several minutes.
When is the equilux in Canada?
The equilux occurs slightly earlier in Southern Canada and later in the North. Here are some dates around where this occurs, though the exact timing may vary slightly.
Calgary, Edmonton, Regina, Winnipeg, Vancouver, Victoria, Toronto, Ottawa, Montreal, and Halifax: March 17
Yellowknife and Iqaluit: March 18
By the time we reach the equinox on March 20, places like Toronto will already be experiencing about 12 hours and 10 minutes of daylight, and that number grows even more for northern communities.
Daylight gains: A rapid increase
One of the most exciting aspects of the equinox is the rapid increase in daylight hours.
Around this time of year: Cities in Southern Canada gain about three minutes of daylight per day.
In Northern Canada, places like Yellowknife, N.W.T., gain about six minutes per day.
This acceleration in daylight gain makes a big difference, especially in regions that endured months of early sunsets and long winter nights. Well deserved, Canada.
A spring warm-up?
The return of longer days also brings a boost in temperatures. As we head toward the astronomical start of spring, some areas of Canada are seeing a taste of warmth:
In southern Ontario and Quebec, temperatures are exceeding double digits this week. The Prairies are seeing milder air work into their forecast with above-freezing temperatures.
In British Columbia, the temperatures have gotten the memo just yet, with some chilly air lingering over the province.
For many Canadians, this is the first signal that winter’s grip is loosening––whether or not the snow agrees.
Bottom line
The equinox and equilux are often confused, but now you know why they’re different!
Thanks to Earth’s atmosphere and the way light bends, we get a little bonus daylight, making the equinox feel less like a perfect balance and more like a turning point toward longer, brighter days.