Hot and gusty overnight conditions have fanned flames in Victoria’s Gippsland region, forcing urgent evacuations of residents in the path of “unstoppable” bushfires – and flooding could be next.

Emergency warnings were issued for Stockdale, Iguana Creek, Glenaladale, Briagolong, and coastal Seacombe as fires burned out of control on Monday night.

Residents were advised to “leave immediately” or prepare to leave as hungry flames jumped across roads and marched towards communities.

Some areas were warned to brace for fires within the hour.

However, the emergency could soon go from fire to flood. A different low-pressure system is expected to dump heavy rainfall and spark flash flooding from Wednesday.

Victorian Country Fire Authority chief officer Jason Heffernan said the change should provide much-needed relief. But it would only pause the fire risk in the Gippsland area after a warm and dry start to the season.

“At the moment we’ve got a fire situation affecting families in East Gippsland, and then not 24 hours later an emergency rain event affecting those same communities.”

Tweet from @CFA_Updates

Victoria State Emergency Service’s Tim Wiebusch said the area from Bairnsdale to the NSW border would be the hardest hit by heavy rain. Moderate flooding is expected for the Mitchell, Tambo, Snowy and Genoa rivers.

Wild winds from a predicted cold front made fire-fighting efforts challenging on Monday night into Tuesday morning.

The largest fire front was 5000 hectares in difficult terrain north of Maffra in the Briagolong, Culloden, Moornapa and Stockdale regions.

Heffernan said the next 24 hours would be testing, with winds associated with a cold front to make things difficult.

Earlier, the weather bureau warned a cold front would bring damaging wind gusts from 4pm Monday to early Tuesday morning – the most damaging before 6am.

Extreme danger for Sydney

Dry heat and strengthening winds mean Sydney and NSW holidaymakers on also high alert for bushfires as more than 100 blazes burn statewide.

Greater Sydney and greater Hunter are among five areas facing extreme danger from blazes on Tuesday, and among eight areas subject to total fire bans.

Tamworth, Dubbo and tourist hotspots of Batemans Bay and Merimbula are among other centres facing increased fire risk.

The warning for elevated fire danger came as the Bureau of Meteorology forecast above-average temperatures and winds becoming strong and gusty along the coast and southern half of the ranges on Tuesday.

Sydney is forecast to surge to a top temperature of 33 degrees.

The risk became real on Monday afternoon for communities north of Mudgee, where residents were told it was too late to flee a fast-running grass fire.

Those still in the St Fillans were told to shelter while people further south in Eurunderee and Budgee Budgee were told to travel to Mudgee if unprepared.

Water bombers and firefighters gained control of the blaze late on Monday afternoon, easing the threat to homes.

“If you do not have a plan, decide what you will do if the situation changes,” the NSW Rural Fire Service warned.

“Leaving early is your safest option.”

All other 107 blazes statewide on Monday night were burning at advice level.

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Island blaze

Firefighters are being sent to an island in Bass Strait to help battle an out-of-control bush blaze threatening shacks and homes.

An emergency warning was issued on Monday afternoon for the communities of Pine Scrub and Leeka on Flinders Island.

Tasmania Fire Service deputy regional chief Steven Richardson said the bushfire sparked from a fuel reduction burn done last week. He said firefighters based on the island were working to contain the blaze, along with helicopters.

Mr Richardson said more firefighters would arrive on Monday night and Tuesday.

“Some of these properties [at risk] are in dense bush and we have to be realistic that we may not be able to protect all of them,” he said.

Leeka is a small rural community on the north-west coast of the island, with a population of about 900.

There are more than 20 properties in the area. Some residents have evacuated while others have decided to stay and fight the fire.

“If your home is built using contemporary bushfire design standards, is well prepared and you can actively defend it, it may provide shelter,” the warning said.

“If your home is unprepared, go to a safer location now only if the path is clear and safe.”

Mr Richardson said visibility was poor in the area because of smoke.

-with AAP