A tornado watch and a severe thunderstorm warning have ended for the Ottawa area as of early Tuesday evening.

The tornado watch covers Ottawa, Gatineau, Smiths Falls, Lanark, Sharbot Lake, Brockville, Leeds and Grenville, Renfrew, Pembroke, Barry's Bay, Cornwall, Morrisburg and Prescott-Russell.

"The main threats with these thunderstorms are large hail, damaging wind gusts and torrential downpours," Environment Canada said in a notice posted on its website.

"The threat for isolated tornadoes is expected to develop later this morning and continue through much of the afternoon. This is a dangerous and potentially life-threatening situation. Be prepared for severe weather. Take cover immediately, if threatening weather approaches."

An Ottawa police officer directs traffic around downed trees on the Airport Parkway Tuesday morning. (David Richard/Radio-Canada)

Trees down near Ottawa airport

A powerful thunderstorm that moved through Ottawa Tuesday morning brought hail and heavy rain, and took down trees along the Airport Parkway not far from the Ottawa International Airport.

The parkway was reduced to one lane from Walkley Road to Hunt Club Road as crews removed debris, but has since fully reopened.

Highway 174 in east Ottawa is closed from Trim Road to Quigley Hill because a tree fell onto hydro wires. The duration of the road closure is unknown.

Firefighters dealt with 11 storm-related alarm calls caused by lightning, power outages, fallen trees, an elevator rescue and three pole fires.

The day will remain muggy under mostly cloudy skies.

The high temperature is expected to reach 27 C, about 3 degrees above average.

Wednesday is shaping up cooler and leading to a more calm, clear and cooler end to the week.