Residents of an apartment building in Kelowna had a close call after water from Mission Creek began pushing through a 30-year-old retaining wall. (CBC)

Emergency co-ordinators in the North Okanagan are warning people living along the Shuswap River to be ready to evacuate their homes.

Environment Canada forecasts 20 to 50 millimetres of rain will fall in the Shuswap region by Sunday. The B.C. River Forecast Centre has added the Shuswap and South Thompson rivers, and Mission Creek in the Okanagan to a list of waterways under a high streamflow advisory.

"The Shuswap River remains really a concern for us because with that amount of water coming in, especially the levels from Mabel Lake right through to Mara Lake, that could cause significant rise and enough to cause flooding in that area, especially around the mouth where it goes into Mara Lake," said emergency co-ordinator Gord Molendyk.

Molendyk said people living along the river need to be prepared for the worst.

"It could come up quickly, so the emergency operations centre is advising property owners in those areas prone to flooding to move your livestock to higher ground," he said.

"And if you're in an area that has flooded before, sandbag your property and we're saying be prepared to evacuate if necessary."

The advisory already covered several other rivers, including the Upper Fraser, North Thompson, Nechako, Cariboo and Bella Coola.

The forecast centre says the rain combined with melting snow could raise some waterways to flood stage, including the Fraser at Prince George and the Bella Coola River on the north coast.

With files from The Canadian Press