LETHBRIDGE, ALTA. -- A powerful wind storm swept through Alberta Wednesday, knocking out power, breaking trees and forcing two Lethbridge School districts to send students home before lunch.

Throughout much of the day city crews worked to restore electricity, clean up broken tree branches and remove debris left behind by the high winds.

The storm was triggered by a huge low pressure system that swept across western Canada and the United States, sucking cold air in behind it, and leaving most of southern and central Alberta under a wind warning.

Environment Canada said the wind gusts reached 137 kph at Barnwell, just west of Taber.

In Taber, firefighters combed the streets, and helped to assist residents dealing with damaged roofs, fences and trees.

The wind made driving dangerous. One semi-truck was toppled near Coalhurst Tuesday, and RCMP said trucks were also blown off Highway 2 between Fort Macleod and Claresholm.

There were no reports of serious injuries.

Lethbridge windstorm

In some areas the wind was accompanied by rain, freezing drizzle and even hail.

According to the city, the high winds caused two major power outages that blacked out more than 1700 homes, and left much of downtown Lethbridge without electricity.

In parts of south Lethbridge, the wind snapped off the tops of trees, which fell onto power lines.

It also knocked over garbage and recycling bins that had been placed out for collection.

By noon, power to most parts of the city had been restored, but by then thousands of school children had already been sent home.

Lethbridge windstorm

Lethbridge Public School Division Superintendent Cheryl Gilmore said deciding to close schools due to a facility concern is never an easy decision, but there are two key factors that the district considers.

“Number one, how long has the school been without that necessity, in this case electricity,” added Gilmore.

She said they also take into account how many schools are affected, and try to find out how long the outage will last.

“After 90 minutes we try to make a decision,” she said, pointing out toilets don’t flush and the air circulation system isn’t working properly.

School officials made the call to send kids home after learning the power outages could last anywhere from one to five hours.

“Inevitably it seems to be when you make the decision, then the power comes back on.”

Fortis Alberta said crews were working to restore power to another 1,300 customers in the areas east and south Lethbridge, including almost 700 homes in the Milk River-Warner area.