Members of the Canadian Armed Forces are headed to B.C.'s flood-ravaged southern Interior, as thunderstorms threaten to send raging rivers surging even higher.

On Thursday, Public Safety Minister Ralph Goodale announced he has approved the province's request for assistance, and that the federal response will include help from the military.

"Troops are deploying to the affected areas and will provide assistance with evacuations, help protect key assets from flood damage, and bolster sandbagging efforts," Goodale said in a statement.

"British Columbians can rest assured that help will be provided as soon as possible."

The first troops are expected to arrive in Vernon Thursday night, and should receive a warm welcome in communities that have largely relied on volunteers to fill and transport tens of thousands of sandbags.

In Grand Forks, elementary school children were even excused from class in shifts this week to help out. Deputy Fire Chief Kevin McKinnon said the work does seem to have taken a toll on stressed and exhausted locals.

"You have to assume they are starting to feel the strain and the tiredness," McKinnon said. "Having fresh bodies, extra bodies coming in from the military is going to be a huge plus for them."

The military support is just one aspect of the federal government's support, according to Goodale, but further details have not been provided. The minister said the Government Operations Centre is in the process of coordinating federal and provincial agencies.

Meanwhile, Environment Canada has put much of the southern province under special weather statements, cautioning that thunderstorms could deliver as much as 40 millimetres of rain by late Friday.

There are concerns that downpours could increase the flood risk in areas like Grand Forks, which is still reeling from widespread property damage caused by last week's flooding.

All schools in the city were closed Thursday over the potential for additional flooding and road closures. 

Evacuation orders have forced about 3,000 people in the area from their homes, and the Regional District of Kootenay Boundary has cautioned even more evacuations could be necessary along the Kettle River watershed due to sloughing and erosion of the riverbanks.

"Anyone whose home is on a riverbank and who is concerned about sloughing or bank failure should stay clear," the district said in a news release.

"It is extremely important to be safe when near floodwater. River levels can rise quickly and currents can be unpredictable. The ground can be soft and unstable causing extremely poor footing. Exercise extreme caution."

Evacuees have been on tenterhooks worrying about their homes, but were given an unexpected surprise Thursday when officials allowed them a 12-hour window to return, gather their belongings and put down sandbags.

June Berkiw, 82, was forced to leave home three days ago, and coming back was bittersweet. She fears waste from a septic tank has flooded into the property, potentially rendering it unlivable.

"This is what I'm worried about, it's the bacteria from the mold," she said. "The pollution from the broken sewer pipes in Ruckle contaminating all the water. People who are on well I wouldn't even want to drink their water right now."

A state of local emergency remains in effect across the entire neighbouring Regional District of Okanagan-Similkameen, which posted on its website that provincial agencies are closely monitoring the levels of Osoyoos Lake and preparing for evacuation orders if required.

In the Regional District of Central Kootenay, east of Grand Forks, evacuation alerts were expanded along Erie Creek and the Salmo River, while firefighters from across the district were sent to the village of Salmo to help with sandbagging in anticipation of flooding there.

With files from Sarah MacDonald and The Canadian Press