A summer day on the Hudson is off-limits for now.

Westchester County health officials are warning residents to stay out of the river after a power failure at Yonkers’ wastewater treatment plant sent sewage into the waterway — just as thousands of people were heading outside for holiday weekend recreation.

The advisory, first issued Friday, July 3, was expanded Tuesday, July 7, after officials said contamination concerns remained following the plant failure and were worsened by runoff from Monday’s heavy storms. No end date has been announced.

The warning applies to all activities involving contact with Hudson River water, including swimming, kayaking, paddleboarding, fishing from the water, boating that involves entering the river, and full-body immersion. Phillips Manor Beach Club in Sleepy Hollow remains closed.

Although Rye, Harrison, and Rye Brook sit along Long Island Sound, many local residents head to Hudson River communities for summer boating, fishing, and paddling. The advisory covers the entire Westchester County stretch of the river.

The Yonkers Joint Water Treatment Plant serves roughly 505,000 people across 22 municipalities and typically processes about 100 million gallons of sewage each day. Officials have not released how much wastewater entered the Hudson during the outage.

The failure came during a week of extreme weather. Storms over the July 4 weekend knocked out power to more than 170,000 Con Edison customers across the region, followed by heavy rain Monday that created additional runoff concerns.

County officials say they are monitoring water conditions and will provide updates when the advisory changes. Until then, residents should avoid contact with the Hudson River.

Questions can be directed to the Westchester County Department of Health’s 24-hour public health information line at 914-813-5000.