The sixth annual Levi’s GranFondo takes over west Sonoma County on Saturday with a sold-out peloton of about 7,500 cyclists.

The charity ride sends cyclists onto some of the county’s most challenging and scenic roads. GranFondo cyclists choose one of three rides, the 32-mile piccolo, a 65-mile medio and the gran route that travels along 103 miles and climbs more than 9,000 feet.

Motorists should prepare for closed roads and congestion along the route.

A sea of cyclists set out at 8 a.m. from a starting line at the Finley Center on West College Avenue at Stony Point Road. Officials are closing northbound Stony Point Road in the area as early as 1 a.m.

A rolling series of road closures and traffic controls will be in place throughout the route, which roughly travels from Santa Rosa to Graton, through the Russian River communities of Monte Rio and Duncans Mills, into the hills of Cazadero north to Salt Point State Park and back along Highway 1 on the Sonoma Coast and through Occidental to Santa Rosa.

Cyclists should prepare for hot weather. Temperatures are expected to be in the 90s for an early-autumn heat wave.

Ride organizers are concerned that riders be prepared, spokesman Greg Fisher said.

“Riders are going to have to start hydrating early and often,” Fisher said.

Last year, the GranFondo pumped about $3.15 million into the local economy and raised about $277,000 for local nonprofits, including its primary beneficiary Forget Me Not Farm, a working farm for at-risk children and abandoned animals.

For a full list of road closures, visit http://www.levisgranfondo.com/info/roads.

You can reach Staff Writer Julie Johnson at 521-5220 or julie.johnson@pressdemocrat.com. On Twitter @jjpressdem.