Manitoba and Saskatchewan are looking for a break in the clouds and relief from the torrential rainfall that has flooded many communities, but that's not likely to come for another couple of days.

Environment Canada has a rainfall warning in effect from Regina east to the Manitoba border. Another 15 millimetres are expected to fall across the areas hit hardest on the weekend.

Heavy downpours could cause flash floods and submerged roads, the weather agency has warned. The rain should taper off later Monday afternoon.

In southwestern Manitoba, however, the sun won't likely be seen until late Tuesday or Wednesday. Environment Canada expects 10 to 15 millimetres of rain on Monday and a 60 per cent chance of more rain Tuesday.

Manitoba and Saskatchewan

Western Manitoba and eastern Saskatchewan were hammered by rain on the weekend, with some communities seeing 100-200 millimetres. Shown are some of the affected communities. (CBC)

The Manitoba government says it will open the Red River Floodway on Tuesday morning to protect homes in Winnipeg from the overland flooding.

Officials say they are concerned about the capital city as river levels continue to rise due to the excessive rainfall.

Due to the overland flooding and road closures, mail service has been cancelled for many rural communities in southwestern Manitoba and southeastern Saskatchewan.

Canada Post issued an alert Monday morning, noting that "mail delivery will resume as soon as it is safe to do so."

States of emergency

States of local emergency are in effect in 33 municipalities in Manitoba, and 37 communities in southeastern Saskatchewan.

Some areas got more than 200 millimetres of rain over the weekend, and overland flooding has forced the closure of several roads in both provinces.

In Saskatchewan — in particular Regina and Yorkton — the sanitary and storm sewer systems are taxed to the limit, prompting Regina's fire department to urge people not to shower or even flush their toilets.

At least two people were spotted kayaking down residential streets in Regina, where more than 90 mm of rain fell on the weekend.

The underpasses in the city filled with water Sunday and several drivers had to abandon their cars. No one was hurt.

Helicopter rescue

East of Regina, emergency officials pressed a private helicopter into service Sunday to rescue a group of people stranded on Highway 55 near the Manitoba border.

According to Duane McKay, director of emergency measures for Saskatchewan, the group of four had been marooned by floodwater.

"They came to a washout in the road and they turned around to go back and the culvert they had driven over had washed out, so they were trapped in the middle of the road," McKay said. 

In Brandon, Man., the airport shut down all flights in and out of the city on Sunday after the main access road became impassable owing to the water.

But on Monday, airport staff set up a circuitous detour to get passengers to the building and WestJet announced it was resuming some flights.

Detour signs are being put up along the Trans-Canada Highway and Highway 10, and airport staff will be out to direct traffic.

Volunteers and municipal crews have been out sandbagging in many communities around Manitoba — mostly in the southwest corner but also in the Whiteshell cottage country — trying to protect homes from rising rivers and creeks.

The rainfall amounts weren't as heavy in Winnipeg — 50 mm compared to 151 mm in Deloraine — but the city was battered by wind.

The gusts hit 81 km/h at times and a city spokesperson said Monday that some 400 calls came in about toppled trees or branches.

Meanwhile, CN Rail said the wet weather is affecting train service on branch lines, particularly in the Canora and Humboldt areas in eastern Saskatchewan.

There has also been at least one washout along a branch line, the company said.