More than 60 were flashing red Thursday morning.
The City of Windsor and Enwin are trying to determine what happened Thursday morning with dozens of traffic lights in the city.
Executive Director of Operations Dwayne Dawson says more than 60 traffic lights went into a "fail safe mode" which is when they begin flashing red.
"We had our lights system did experience some power issues, be it a power outage for a short period or power spike or something that interrupted the normal power to the signals," he says.
He doesn't know if it was weather related, but he says city officials are baffled and want to find out the root cause of it.
"All we know right now is that there was some type of power issue or interruption that caused our signals to go into that mode and we are still investigating with ENWIN to see what happened specifically."
Dawson admits this was rare and hopes it is a "one off".
"For it to affect that many intersections is unusual," he says. "Usually you get a small area in the city if there is a problem, but this was wide-spread so this is a larger number than we would normally see."
Dawson says the final traffic lights were functioning normally around 11:30am.
Walker and EC Row. Traffic lights affecting things in all directions. Avoid if you can, because I can't seem to get out lol #cklw pic.twitter.com/VerXDw6zfV
— Kimberley N Johnson (@KimberleyNJ) November 2, 2017