Nova Scotia Premier Darrell Dexter called the damage from days of heavy rains in the province "incomprehensible" and pleaded with the federal government for help repairing water-logged homes, collapsed bridges and washed-out roads.

Dexter flew over the flooded regions of southwestern Nova Scotia Wednesday afternoon, surveying the damage caused by as much as 300 millimetres of rain that fell between Friday and Tuesday.

Flood levels began to recede in some areas Wednesday, but dozens of families are still not allowed to return to their homes.

"To say that it's incomprehensible may actually be an understatement," Dexter told reporters.

"The simple reality is that we haven't seen these kinds of severe and regular weather events for, well, forever."

Dexter said engineers will make it a priority to repair the 20-metre Tusket River bridge on Highway 3, which collapsed on Tuesday night.

The 100-year-old metal bridge, used by local traffic to access the highway, was completely removed from the road.

The bridge was located downstream from the Tusket dam, which utility crews have been monitoring closely for signs of possible breaches. So far it has held.

Dexter said he spoke with Defence Minister Peter MacKay, a Nova Scotia MP and a special representative for the province in cabinet, about the province's need for federal help.

"I think it will certainly be in the millions," Dexter said.

"There are an extraordinary number of homes affected, from flooded basements through to structural damage. All of that has to be assessed."

In a statement, MacKay said the government's "thoughts and prayers are with those whose homes and lives have been affected by the flooding."

MacKay said federal disaster assistance is the "subject of ongoing assessment."

Dexter said the damage appeared worse than what was suffered by the Cape Breton community of Meat Cove, where rains and flash floods last summer resulted in more than $7 million in damage to roads, bridges and culverts.

Dexter said current building standards for bridges and roads are adequate for the weather that hits the province. But older infrastructure is aging and "built to different standards," he said.

Officials to assess damage

Environment Canada is forecasting clear skies through the weekend, but Nova Scotia's Emergency Management Minister Ramona Jennex said it's too early yet to say the threat has passed.

"Even though the weather might look promising over the next couple of days we're still monitoring and watching and I wouldn't say we're out of the woods yet. Maybe in a few days we'll be able to say we're on the other side of it," Jennex told CTV News Channel.

Jennex said the province has "no idea" at this point how extensive the flood damage is province-wide.

Dexter has said it could take weeks for provincial officials to fully assess the damage. Many residents have been forced out of their homes and are staying with family and friends.

The assessment process can't even begin until water levels drop, Jennex said.

"A lot of this water is moving, it's not just standing still and we don't know until that water is gone what we'll find underneath."

With files from The Canadian Press