Three girls make their way across the Mayor Magrath Drive underpass in Lethbridge after a downpour overwhelmed storm sewers Tuesday. (David Rossiter/Lethbridge Herald)

Lethbridge declared a state of emergency after a sudden rainstorm blew off manhole covers and flooded basements in the southern Alberta city on Tuesday.

More than 45 millimetres of rain fell in about 90 minutes in the afternoon, overwhelming storm systems in the city, about 200 kilometres south of Calgary.

"It looks like ... what caused it was quite an intense upper low moving from northwest to southeast in southern Alberta," said John McIntyre, a meteorologist with Environment Canada. "It is a lot of rain in a short time."

Lethbridge normally receives 47 millimetres for the whole month, he said.

The intense downpour flooded parts of Lethbridge. (Submitted by Melissa Dittrich)

Late Tuesday, the city gave the green light for residents to return to regular water usage after asking them earlier to refrain from using their dishwashers, showers and washing machines, as well as from flushing toilets, until the storm systems had a chance to clear.

Officials had also requested that people avoid driving on the flooded roads, said Mike Ross, deputy chief of support services for Lethbridge Fire and Emergency Medical Services.

"We had one cloud over the city that just downpoured on us and we ended with torrential rain pour for a good 45 minutes to an hour, and then that set off the flooding," said Lethbridge regional police Staff Sgt. Darcie James.

Manhole covers were blown off, and three of the city's major underpasses were all under water, she said.

The city declared a state of emergency after the two-hour storm. (Submitted by Melissa Dittrich)

"We had to close a bridge leading to the west side where people have access, and that was closed down. And then we have flooding in basements and then residential areas," said James.

Mayor Bob Tarleck declared a state of emergency due to the heavy rain, high winds and flooding, which means the city has the authority to close roads and shut down facilities as it sees fit.

Transit service was suspended for several hours Tuesday afternoon, and fireworks to celebrate Canada Day were cancelled.

The record rainfall in Lethbridge on Canada Day is 63.5 millimetres and was set in 1982.

With files from the Canadian Press