The Head of the Charles is officially underway.

The largest rowing regatta in the world is bringing 12,000 competitors from more than 40 countries to the Boston area. The event began Friday and continues through Sunday.

“This is a winding course that really brings the best out of rowers in terms of their ability to steer and to make turns to pass other rowers as they go by to navigate bridges,” said Head of the Charles Chief Operating Officer Blair Crawford. “And it just brings a whole new set of challenges that is not typical in the majority of racing.”

Spectators and competitors will be greeted with unseasonably warm conditions. The National Weather Service forecasts a high temperature of 70 degrees on Saturday and 72 degrees on Sunday, with sunshine and calm winds both days.

“Unlike last year, it’s going to be just a wonderful weekend. I mean, unseasonably warm,” Crawford said.

He recommends walking or taking public transit to one of the many viewing spots along the three-mile course. Parking near the river is extremely limited.