Thunderstorms are expected to bring further heavy rain over the coming week as government agencies battle to pump out excess water from the Wainfleet area.
Around 130 homes were flooded after the River Steeping burst its banks last week, leading to the evacuation of around 590 properties in total by Saturday afternoon.
RAF Chinook helicopters have dropped more than 330 one-tonne sandbags in an attempt to repair the riverbank and police drones are monitoring the area to look out for any further breaches of flood defences.
The Environment Agency installed two ”Ultra High Volume” pumps to help remove water from the affected areas.
But it also warned that there was an increased risk of flooding between Tuesday, Wednesday and Thursday due to new Met Office weather warnings covering the east Midlands.
Forecasters are predicting up to 50mm of rain in some areas, with between 15mm to 30mm over the wider region.
It comes on top of the 132mm - more than two months worth of rain – between 10 and 12 June, described by the Environment Agency as an “unprecedented event”.
“River levels are expected to remain very high for the next few days,” the agency said in a statement. ”Our staff are out in the area assisting the military, emergency services and council. “Military aid has assisted in stemming the flow from the river. The repair is still holding and we’re still out on the ground today. Remain safe and be aware of your local surroundings.”
Lincolnshire Police initially told residents they should be prepared to be away from their homes for around 48 hours – but the risk of further flooding may extend this until Friday.
Local MP Matt Warman said environment secretary Michael Gove had assured him officials would “have access to every resource they need regardless of cost” to protect lives and homes.
He added: “In terms of the response, we have seen an incredible working together of the agencies. Local people should keep an eye on the police updates because there is still the potential for risk to homes and lives. But in the long term, it will always just be a huge thank you.”
Lincolnshire Police have issued a list of nearly 100 postcode in the PE23 and PE24 area where evacuations are possible.
In its latest update on Sunday afternoon, the force advised people in Wainfleet not to use their washing machines, toilets or showers and suggested they use portable facilities set up in the town.
A total of 13 flood warnings and 23 flood alerts are in force across the country, according to the Environment Agency website.
Additional reporting by Press Association