THAMESVILLE, ONTARIO, Canada -- A community in southwestern Ontario has declared a state of emergency due to the imminent threat of flooding along the Thames River.

Chatham-Kent Mayor Randy Hope requested a voluntary evacuation of the community of Thamesville, Ont., about 95 kilometres south of London, Ont., Friday morning.

He said the Lower Thames Conservation Authority indicated the Thames River was expected to peak near the town by the evening, and urged residents to prepare to leave as soon as possible.

The conservation authority issued a flood warning Thursday night and said that it would remain in effect until Saturday.

Hope says in a statement that a local convention centre opened Friday at noon as an emergency shelter for residents who aren't able to stay with friends or relatives in unaffected areas.

Days of mild temperatures and heavy rain has caused flooding in other parts of southern Ontario this week, including Brantford, Ont., and Orangeville, Ont.

The city of Brantford issued a state of emergency Wednesday when warm weather and torrential rain caused an ice jam on the Grand River, forcing nearly 5,000 people from their homes.

About 100 kilometres away in Orangeville, a three-year-old boy went missing in the Grand River on Wednesday when fast-moving waters swept him away from his mother's grip after their van plunged into the water.

In the Thamesville area Friday afternoon, gas was being shut off at affected homes and businesses as a safety precaution.

"We need residents to leave sooner rather than later in case the situation deteriorates," Hope said in a statement.

"We are asking residents to take a 72-hour supply of medication and personal items with them since the water may remain high for several days."

Ontario Premier Kathleen Wynne said in a tweet Friday that her thoughts are with the people in the affected communities.

"Ontario will support you during this emergency and as you rebuild and recover," she said.