Thursday's Vernal Equinox ushers in Spring across Canada for 2025
While meteorologists started spring a bit early, the rest of us are about to catch up!
We welcome the end of Winter and the start of Spring for 2025 this week, and there's a chance we could soon see vibrant auroras due to a phenomena known as 'equinox cracks'.
On Thursday, March 20, the Sun crosses the Celestial Equator, headed from south to north.
A view of the equinox from space, courtesy the GOES-13 geostationary weather satellite, on March 20, 2013. (NOAA)
The exact timing depends on how you set your clock:
6:31 a.m. NDT,
6:01 a.m. ADT,
5:01 a.m. EDT,
4:01 a.m. CDT,
3:01 a.m. MDT/CST, and
2:01 a.m. PDT.
This event marks the moment of the Vernal Equinox, when the Spring season starts in the northern hemisphere for 2025.
Visit our Complete Guide to Spring 2025 for an in-depth look at the Spring Forecast, tips for planning for it and much more!
The reason for the seasons
Although we talk about the Sun 'crossing' a line at the start of spring, the Sun doesn't actually move anywhere relative to our planet.
Instead, the Sun appears to move in our sky, higher and higher each day from Winter Solstice to Summer Solstice, and then lower and lower each day from Summer Solstice to Winter Solstice, due to Earth's tilt.
As our slanted homeworld travels along its orbit, with its north pole always pointed towards the star Polaris, that 23.4 degree tilt causes the northern hemisphere to be pointed more towards the Sun between late March and late September. With the Sun higher in the sky, each photon of sunlight travels through less atmosphere to reach the ground, and they arrive there with more of their energy, making those the warmer months for the northern hemisphere. From late September through late March, it's the opposite. The angle of the Sun gets lower, causing the photons to travel through more atmosphere to reach the ground, and they arrive with less energy, thus making it colder.
In the southern hemisphere, they experience this same trend, but at opposite ends of the calendar — colder from March through September, and warmer from September through March.
In between those periods are two exact moments when the Sun illuminates the surface of both hemispheres equally. These are the equinoxes.
These four views of Earth from satellites in space show our planet, from left to right, during the northern summer solstice, fall equinox, winter solstice, and spring equinox (NASA)
The exact timing of the equinoxes changes from year to year, but in 2025, the northern hemisphere's Vernal (Spring) Equinox and the southern hemisphere's Autumnal (Fall) Equinox, occur on March 20, at 9:01 UTC or 5:01 a.m. EDT.
DON'T MISS: What's the difference between "astronomical spring" and "meteorological spring"?
Equinox Cracks?
The Sun and Earth are each surrounded by their own magnetic field. The Sun's magnetic field not only creates a safe 'bubble' around our solar system, but it also contributes to solar activity, such as solar flares and coronal mass ejections (aka solar storms).
The Earth's magnetic field reacts to these solar storms, and to the flow of the solar wind, which results in coloured displays across our sky known as the Aurora Borealis, or the Northern Lights. Similar displays are seen around the south pole, known as the Aurora Australis or the Southern Lights.
Auroras appear around the north and south poles of Earth as Earth's geomagnetic field traps particles from the solar wind and funnels them down into the atmosphere. (NASA)
READ MORE: Why are the Northern Lights so supercharged lately and how long will this last?
Due to Earth's tilt, our planet's magnetic field is nearly always out of alignment with the Sun's magnetic field. So, even under the absolute ideal conditions for a solar storm or the solar wind to result in auroras, that misalignment effectively reduces the overall intensity of any aurora display that does appear.
However, around the equinoxes, the magnetic fields of the Sun and Earth line up better than they do during the rest of the year.
The orientation of Earth's magnetic field at northern summer solstice (left), equinox (centre), and northern winter solstice (right). The Sun is located far off the left side of the field of view, and its magnetic field is oriented most in alignment with the centre panel. (NASA/Scott Sutherland)
This alignment causes the two magnetic fields to form strong connections with each other, which opens up 'cracks' in Earth's magnetic field. These cracks then allow more particles from the solar wind or from solar storms to stream down through that protective barrier and into upper atmosphere.
As a result of all this, auroras that occur around the spring and fall equinoxes can be some of the brightest and most colourful of the entire year!
This colourful aurora display was captured by Tree and Dar Tanner from central Alberta, on March 23, 2023. (TeamTanner)
According to NOAA's Space Weather Prediction Center, aurora activity has been quiet over the past few days, and this looks to continue through Thursday night. However, NRCan's Canadian Space Weather Forecast Centre has recorded some active to stormy conditions over the past 24 hours (they look at hourly conditions instead of 3-hour, like SWPC), and they are predicting unsettled to active auroras throughout northern and central regions of Canada (extending down through the central-Prairies) over the next 24 hours.
Watch for any solar storms erupting from the Sun in the coming days, though. It could result in an explosion of colour across our night skies!
(Thumbnail image shows the moment of the vernal equinox, on March 19, 2020, as seen from the GOES-East geostationary weather satellite. Courtesy: NOAA)