Eastern Ontario and western Quebec are dealing with damage caused by lines of severe thunderstorms with gusts of up to 140 kilometres an hour.

Ottawa police said they responded to almost 300 calls between 7 and 9 p.m. Sunday that ranged from power outages to stranded boaters to trees and signs blown over.

Ottawa Fire Services spokesman Marc Messier said they responded to as may as 180 storm-related calls which included one working fire and eight water rescues.

He said a fire on a back deck caused $20,000 of mostly external damage to a rowhouse unit at 558 Gladstone Avenue, with no injuries reported.

A woman in her 40s was reportedly struck by lightning in the upper Pontiac region. She was taken to hospital with unknown injuries.

A piece of the roof of Enriched Bread Artists on Gladstone Avenue was torn off, crushing two cars underneath. There are no reports of injuries in that case.

"We did hear a sound and we weren't sure what it was," said Karen Jordan, an artist at the studios who lives nearby. "It sounded like a bang and something else."

The storm also ignited a fire in a Pembroke apartment after its roof was struck by lightning.

There are widespread power outages affecting more than 30,000 residents, with many trees and power poles down.

"The city said they're getting on it as fast as possible but there are also multiple trees down in the area," said one resident in front of the Greyhound station in Ottawa's Centretown neighbourhood.

The Ottawa International Airport experienced a few delayed arrivals and a power outage, but managed to avoid widespread disruption.

There were still severe thunderstorm watches in effect for Ottawa, Gatineau, Cornwall, Smith's Falls and Brockville, as well as for Upper Gatineau, the Pontiac, and Pembroke early Monday morning.

Afternoon heat wave

Earlier, the region sweltered under heat and humidity advisories Sunday, as the humidex soared into the 40s in some areas.

Environment Canada had issued a high heat and humidity warning for much of west Quebec, including the Pontiac and Upper Gatineau.

They said the humidex in those areas could peak at 42 degrees in the afternoon.

With a report from CTV Ottawa's Stefan Keyes