Southern Australia suffered Friday from a record-breaking heat wave that has threatened rural towns with wildfires and sent ambulance crews after heat-stressed patients.

Melbourne, Australia's second-largest city recorded its third consecutive day of temperatures above 109 degrees for the first time since 1855, when record-keeping began, the Bureau of Meteorology said.

Authorities blame the heat for a significantly higher than average number of sudden deaths, News.com.au reported.

Health Minister John Hill said many of those who have succumbed to the high temperatures are elderly.

"How many of them are associated with the heat is speculative — but it's obviously a high number," he said.

Click here for photos.

The temperature in Melbourne topped 113 degrees on Friday ahead of a cooler change that might even bring some thunder showers, the bureau said.

Adelaide, the other major city on the south coast, is expected to match its longest heat wave in a century by Monday, with six consecutive days exceeding 104 degrees. The heat there buckled train and tram lines.

The high temperatures have afflicted tennis players and spectators alike this week at the Australian Open in Melbourne, where men's No. 3 seed Novak Djokovic retired ill from a game Tuesday after heat-related complaints.

The retractable roofs on Rod Laver Arena have been closed at least parts of the last three days.

There was controversy Wednesday when they closed the roof during the match between Serena Williams and Svetlana Kutzetsova. The Russian had won the first set, but the break gave Williams time to recover and she rallied to win.

Players complained that it felt like their feet were burning right through their shoes. A bunch of moths that have annoyed the players were basically sizzling and dying within seconds of landing on the broiling court surface.

Melbourne is the capital of Victoria state, where three rural towns were under threat from wildfires spreading quickly in the furnace-like conditions, Country Fire Authority deputy chief fire officer Geoff Conway said.

Bureau of Meteorology forecaster Richard Carlyon said firefighters will have to wait for rain to dampen the tinder-dry conditions.

State ambulance service chief Greg Sassella said more crews to help people affected by the heat were available on Friday, a day after 1,305 emergency cases were logged — more than double the normal load.

Click here to read more on this story from News.com.au.

The Associated Press contributed to this report.