Residents have been warned to expect weather similar to the deluge that hit Perth in October 2023.
The Met Office has issued a 48-hour warning for heavy rain across Tayside, Fife and Stirlingshire.
This began at midnight on Monday and ends at 11.59pm on Hogmanay.
Flood alerts have also been issued as persistent and heavy rain continues across the country.
And the Scottish Environment Protection Agency (Sepa has now warned the downpour may echo the weather of October 7-8 2023, when flooding forced Perth residents to flee their properties.
It comes as Perth and Kinross Council announced its floodgates will be shut as a precaution.
Sepa duty flood manager Cordelia Menmuir said: “Extremely high water levels are expected in Tayside.
“This may result in disruptions to transport and to communities.
“We could see similar levels to those experienced in October 2023, when places like Aviemore and Perth were severely affected.
“We’re likely to see extensive river and surface water flooding impacts across these areas.
“We’re already seeing impacts on the road and rail network, and further rain will only exacerbate this.
“We urge people living, working and visiting in the affected areas to consider any steps you need to take now to be prepared for flooding impacts.
“Consider whether your journey is necessary.”
Perth floodgates to be closed
Dozens of properties in Perth’s North Inch were deluged in October last year.
This month, Perth and Kinross Council admitted it was wrong to leave the North Inch floodgates open during the extreme rainfall.
The council also admitted there were too few trained staff on duty to close all the gates in Perth’s £25 million flood defences.
A Perth and Kinross Council statement on Monday afternoon said: “The flood gate at Shore Road, Perth, will be closed at 6pm this evening as a precaution.
“The gate will be staffed overnight to provide emergency access to vehicles.
“The Tay Street Promontory flood barrier will be put in place tomorrow (December 31), as a precaution.
“Most other flood gates in Perth have already been closed today (Monday 30 December) based on the latest information received from Sepa, in line with the Perth Flood Scheme Operational Procedure.
“Sepa has issued five flood warnings for Perth and Kinross.
“All of these warnings say flooding is likely on low-lying agricultural ground.”
Scottish Government’s Hogmanay review
A Scottish Government meeting was due to take place on Monday evening to review preparations for the rain on Hogmanay.
Justice and home affairs secretary, Angela Constance, said: “There is expected to be a significant amount of rainfall in the next 24 hours after a period of wet weather, raising the risks of travel disruption and flooding.
“New year travellers are advised to plan ahead during this normally busy period and follow Police Scotland and Traffic Scotland advice on the roads.
“If you are planning to travel by rail, air or ferry, please check with your operator for the latest service information.
“For information on what to do and stay updated with live flooding updates visit the Sepa website.”
The Met Office warning says rainfall totals of 50mm to 70mm are possible. Some places may see 100mm to 140mm of rain.
Sepa says flooding is “expected” in areas surrounding the Upper Tay.
This includes low-lying areas of Aberfeldy Golf Course, Aberfeldy Caravan Park and agricultural land.
All trains between Perth and Inverness were cancelled on Monday due to high water levels near the railway line in the Kingussie area.
Disruption may continue into the new year, with an 18-hour yellow warning for snow beginning on January 1.
Conversation