A brutal Arctic air mass is settling over the province this weekend, but residents should be prepared for more than just a biting wind chill.
As temperatures forecast to hit a bone-chilling -30 C, a rare and startling winter phenomenon could occur: exploding trees. While it sounds like folklore, the reality is a fascinating (and very noisy) display of winter physics.
This can happen because even in the dead of winter, trees hold onto moisture and sap. When a sudden, extreme deep freeze hits, that sap begins to freeze and expand. If the temperature drops fast enough, the outer bark contracts while the inner wood remains under immense pressure. When that stress finally reaches a breaking point, the trunk splits with a sharp, echoing crack that sounds remarkably like a gunshot or a loud firecracker.
Meteorologists say the conditions right now are the perfect storm for these frost cracks. Because Ontario saw a mix of rain and milder temperatures earlier in the week, our trees are currently quite hydrated.
The arrival of the polar vortex tonight provides the exact flash-freeze conditions needed to trigger these mid-winter booms.
While hearing a loud bang in the forest can be terrifying, it generally isn’t a threat to people. As for the trees, most are resilient and will heal the “wound” during the growing season, often leaving behind a visible scar called a frost rib.
For yourself, while you don’t need to worry about exploding wood, the extreme cold can make larger branches brittle. Stay safe by avoiding standing directly under old, heavy trees during high-wind events.
This phenomenon is so legendary in North American history that some Indigenous cultures, including the Cree and Cherokee, refer to the first mid-winter new moon as the “Moon of the Exploding Trees.”
If you hear a thud that feels like it shook the ground rather than a crack, you might be experiencing a frost quake. This happens when moisture in the soil freezes so rapidly that it actually cracks the bedrock, sending shockwaves through the neighborhood.
Stay warm and keep your ears open tonight, Toronto! If you hear a bang in the woods, it’s just the forest reacting to the deep freeze.