Russian Maria Sharapova and Serbia's Jelena Jankovic waited for a deadly storm to pass before thundering into the Toronto Cup quarter-finals on Thursday.

Sharapova, working her way back to form after nine months away with a shoulder surgery, was first onto a centre court that hours earlier had been evacuated, booking her spot in the last eight with a 6-2, 7-6 win over seventh seed Vera Zvonareva.

"I've had a lot of rain delays but probably none because of a tornado," Sharapova told reporters. "I know there were tornado warnings but I didn't hear much because I was in the players' locker room and we're around cement and that was good."

Sharapova will now play Polish 14th seed Agnieszka Radwanska, who advanced with a 7-5, 6-3 win over Ukraine's Kateryna Bondarenko.

With the clock ticking past midnight, fifth seed Jankovic mopped up a wild night battling to a 1-6, 6-3, 7-5 win over Belgian Kim Clijsters, playing just her second event since having a baby and coming out of her two-year retirement.

The start of the evening session was delayed by an hour as the last of severe weather that set off multiple tornadoes within a few miles of the Rexall Tennis Centre roared across Toronto.

The violent storms, which were being blamed for at least one death, forced an evacuation of the stadium with spectators taking shelter in the basement and the VIP lounges.

Jankovic, winner last week in Cincinnati, will take on 36th-ranked Russian Alisa Kleybanova, who beat France's Aravane Rezai 6-3, 6-4.

World number two Serena Williams avoided all the nasty weather, racing into the quarter-finals with a 6-1, 6-4 demolition of Ukrainian Alona Bondarenko before the storms hit.

Williams needed only 64 minutes on a blustery centre court to dispose of the world number 33 and restore a bit of family honour after the Ukrainian's sister Kateryna had knocked out older sibling Venus in the second round.

Back on centre court just 15 hours after a second round victory over Yaroslava Shvedova, the Wimbledon and Australian Open champion charged to a 5-0 lead on her way to taking the opening set.

Serena next plays Czech qualifier Lucie Safarova, who progressed with a 7-6, 6-4 win over China's Zheng Jie.

"I was trying to be perfect and just couldn't get my serve in. I got frustrated," said Williams, who lost three straight games in a momentary second set wobble.

"I thought I played pretty well yesterday. I was a little disappointed in myself today after playing so well."

Fourth seed Elena Dementieva booked her spot in the last eight with a ragged 6-1, 1-6, 6-4 win over Israel's Shahar Peer.