Just in time for the first big boating weekend of the season, authorities on Tuesday announced that a speed limit of 5 miles per hour will be imposed on a stretch of the St. Croix River near the Twin Cities.

The Washington County Sheriff’s Office said the river’s anticipated cresting above 683 feet by Wednesday will trigger a “no-wake” zone until at least Sunday for more than 50 miles from Taylors Falls south to where it joins the Mississippi River in Prescott, Wis.

The move means that Memorial Day weekend boaters on the St. Croix must limit their vessels to “the slowest possible speed necessary to maintain steerage, and in no case greater than 5 miles per hour,” the Sheriff’s Office said.

Rainfall in the Twin Cities in May has totaled more than 4¾ inches. That’s double what the metro area typically gets at this point, according to the National Weather Service.

A no-wake zone protects boaters from such flood-related hazards as floating debris and river currents. The zone also helps limit damage to shorelines, levees and islands, which are more vulnerable to damage from wakes when the water is high.

Marinas and the Minnesota Department of Natural Resources public water accesses along the St. Croix will have postings up to alert boaters to the restriction.

To the northwest of the St. Croix restrictions, no-wake zones also were announced in Chisago County for East Rush Lake, West Rush Lake, Goose Lake, Robour Lake and Mandall Lake. These zones cover boats within 300 feet from shore.