Environment Canada has issued a rainfall warning for most of the province on Monday, and water levels are expected to rise along the St. John River this week.

The national weather agency said between 25 and 50 mm is expected in parts of the province and possibly higher near the Fundy coast.

Rain will start over the western part of the province and spread in the afternoon. Environment Canada said rain is expected to become heavy at times this evening before ending early Tuesday morning.

Geoffrey Downey, a spokesperson for Emergency Measures Organization, gives an update on flooding in New Brunswick. 1:39

Strong wind gusts will also be travelling between 60 and 80 km/h across New Brunswick. Along the Fundy coast, winds will gust between 90 and 100 km/h, said CBC meteorologist, Tina Simpkin.

Flooding in the forecast

Environment Canada said strong southerly winds and very mild temperatures will accompany the rainfall, resulting in rapid snow melt.

"Heavy downpours can cause flash floods and water pooling on roads," the weather agency said. "Don't approach washouts near rivers, creeks and culverts."

Route 630 is closed between the Fredericton/ Saint John district boundary to about one kilometre south of Route 122 because of a washout. The road is expected to reopen May 1.

According to River Watch, Gagetown is expected to exceed its flood stage of 4.0 metres on Thursday and Saint Hilaire, a village about 10 kilometres south of Edmundston, is also forecast to hit flood stage.

Three communities - Fredericton, St. Hilaire and Gagetown - are forecast to reach or slightly exceed flood stage on Wednesday, April 15, 2020. For the latest flood forecasts, water levels and information go to <a href="https://t.co/YelZRQ4Ll9">https://t.co/YelZRQ4Ll9</a> <a href="https://t.co/rSh291G8rF">pic.twitter.com/rSh291G8rF</a> —@NBEMO_OMUNB

"The river is rising from top to bottom," said Geoffrey Downey, a spokesperson for New Brunswick's Emergency Measures Organization.

Fredericton was originally forecast to hit its flood stage of 6.5 metres by Wednesday. But, according to the government's five-day forecast, which was updated Monday afternoon, water levels will hover around 6.3 metres instead.

How high will the St. John River rise this spring, and does the Mactaquac Dam have anything to do with it? A New Brunswick flood, explained. 1:26

"This is far from over," Downey said. "There is still a lot of snow in the north that's going to melt at some point."

Flooding is caused by factors such as heavy rain, warming temperatures and the amount of snow in the northern part of the province.

"There's a recipe for flooding. It's always there until all the snow is gone," he said.

Residents need to be prepared

Over the last two years, floodwaters reached historic levels along the lower St. John River system, where homes were evacuated, cottages were destroyed and part of the Trans-Canada Highway was closed downriver from Fredericton.

Downey is warning residents to be prepared for the spring freshet, even though water levels don't look as bad as they did in 2018 and 2019.

Ice jams and open-water are the main types of spring floods along the St. John River. 1:35

Downey is advising people to move their belongings from the basement to higher ground. Residents should also tie down loose items on their property, and they should go over an evacuation plan if their home has been evacuated before due to flooding.

Downey says residents should also have a 72-hour preparedness kit.

It should include water, food, battery-powered radio, flashlight, clothes, cash, backup medication and food for pets.

"It could look fine one day and not the next," he said.

Another low pressure system will move into the province on Wednesday, where the province can expect to see rain and high winds.

By the end of the week, Simpkin said New Brunswick will also see a blast of cold air.