Here's why Toronto's night sky glowed mysteriously yellow over the weekend

Toronto's night sky was covered in an eerie yellow glow this weekend, and many people took to social media to snap photos of the strange phenomenon in search of an explanation.

Photographs taken from various points across the city on Saturday and Sunday night show a bright yellow color reflected from the clouds.

Why is the Toronto sky so orange and bright three hours after sunset? I feel like I'm going to the apocalypse right now pic.twitter.com/m34SCDC6cs

— Emma McIntosh (@EmmaMci) February 11, 2024

The multi-night standout, who took to social media for answers, was left confused.

Ok Twitter What does this eerie light in the Toronto sky mean? pic.twitter.com/n3rbHXPD7e

— Nahum Mann (@nahum_mann) February 12, 2024

One user made a funny but totally irrelevant comment.

There's a strange glow in the sky over Toronto's west side tonight…only a blood sacrifice from one of the 351 weed dispensaries will appease the gods. pic.twitter.com/jB6dnFPIl4

— Jonathan (@jtalms) February 12, 2024

Others were looking for the best place to see the phenomenon.

Tired, but went up to the Wallace Bridge to see the mysterious sky glow#Toronto pic.twitter.com/xvd0177RbX

— Celadon Cat of Twitter 🇨🇦 🇱🇹 🇺🇦 (@Celadon_kate) February 12, 2024

So what's the mystery?

#topoli What is the latest theory about GlowTO? pic.twitter.com/VtY75nY4Vz

— John Lorinc (@JohnLorinc) February 12, 2024

Since this phenomenon has been observed several times over the years, the mysterious new glow turns out not to be really mysterious or new.

The BMO Field lights are pictured shortly after the stadium was expanded in 2016. Photo by Jack Landau.

Explanation? That orange glow in the sky is the result of the ultra-bright grow lights used at BMO Field to promote grass growth in Toronto's harsh winters and keep the stadium's hybrid playing field in top condition.

The BMO Field lights are pictured after dark in 2022. Photo by Jack Landau.

BMO Field's occasional nighttime glow has grown stronger in the years since these reports first began flooding. Before more lights were added a few years ago, the stadium painted the night sky yellow, adding to the otherworldly effect.

A strange glow in the sky, west side of Toronto. At first I thought it was a fire. This has been going on all week and I read it was the BMO football field. Apparently every February they use grow lights at night to grow the turf. pic.twitter.com/p4GaMvLpZ3

— Sook In Lee (@sookyinlee) February 12, 2024

The stadium introduced additional grow lights in 2019 to help preserve the natural grass surface and now uses nine large movable lighting fixtures and an additional six smaller fixtures that can cover 65 percent of the field in artificial light and heat.

BMO Field has tn lights lighting up the western sky with an orange glow! You can barely tell it's midnight in this photo, that's how bright they are! #Toronto pic.twitter.com/ORIZc6XA38

— Eric McElroy (@esmcelroy) February 12, 2024

BMO Field will host Toronto FC's home opener on Saturday, March 9 at 2 p.m., when the club takes on Charlotte FC.