Firefighters believe lightning strikes sparked several house fires in Ottawa as Tuesday's early evening thunderstorm tore across the capital.

Lightning strikes are believed to have ignited a fire in the attic of a townhouse on Helmo Crescent in Kanata. The flames then spread to two adjoining units. Damage is estimated at $375,000.

Meantime, a second fire caused $100,000 on Scissons Road in Glen Cairn.

Fire investigators say a third lightning strike hit a gas line leading to a home on Tower Road near Algonquin College in Nepean.

The strike sparked a fire that was quickly put out in the exterior wall of the home before it spread.

On Harvest Valley Avenue in Orleans, firefighters believe lightning struck the roof of a home sparking a blaze that caused $300,000 in damage.

There was also widespread but short-lived blackouts in Nepean, Barrhaven and other neighbourhoods as the storm tracked east.

Planes at the Ottawa airport were grounded until the storm had passed.

In the Upper Ottawa Valley, a viewer snapped a photo of the storm outside Jubilee Lodge Marina in Petawawa. High winds damaged a dock, and the storm began to form what appeared to be a funnel cloud.