As a perfect summer weekend unfolds, many Toronto residents will want to head to the beach to cool off.

But most of Toronto’s beaches  are unsafe for swimming because of elevated e-coli levels – and it’s all because of Monday’s huge storm.

Mark Mattson heads the advocacy group “Lake Ontario Water Keepers.”  He says Toronto’s antiquated sewer system couldn’t handle the sudden deluge on Monday.

Mattson says ” sewer pipes are mixed with the rainwater and when it rains a lot they all explode and discharge the sewage into the streets and right into Lake Ontario.”

E-coli readings at Sunnyside Beach are 17 times above the safety level.

According to the city of Toronto website, the only beaches safe for swimming today are in the east end: Woodbine Beach, Kew Beach, and Bluffer’s Beach Park.