A NUMBER of flights into Melbourne have been stranded on runways in other cities or forced to take diversions interstate as thick fog blankets large parts of Victoria.

For the second day in a row, Melburnians woke to cold conditions with low levels of visibility.

A Qantas flight from Los Angeles to Melbourne is believed to have been forced to land in Sydney because poor conditions at Melbourne Airport.

A man travelling from Tasmania to Melbourne this morning reported his flight was grounded at Launceston for two hours because it was too dangerous to attempt a landing on the mainland.

It's believed a number of Jetstar flights have been cancelled, including one from Sydney to Victoria's Avalon Airport.

The fog is also affecting flights into Tasmania. A passenger on a flight from Sydney to Launceston told news.com.au they had been delayed for more than an hour because of poor weather conditions.

Drivers have been urged to take precautions on the roads this morning, too, meaning the peak hour commute for some will be longer than usual.

The State Emergency Service has asked drivers to drop their speed with some placed experiencing black ice.

"If you hit black ice, avoid accelerating, braking hard or turning the steering wheel quickly," VicRoads said.

"If you try to struggle against the ice by braking hard or steering in the opposite direction, you increase the risk of losing control."

Drivers have been told they should turn on their headlights and contact local councils or police for information on any road closures.

The Bureau of Meteorology issued road weather alerts for all suburbs across Melbourne.

What are conditions like where you are? Let me know: Email rohan.smith1@news.com.au.