A perfect storm of high summer temperatures, a fast moving river and thousands of rafters – some partying with alcohol – Saturday on the American River  has garnered the full attention of law enforcementagencies and rescue organizations.

More than 3,000 rafters are expected to participate in this year’s Rafters Gone Wild event on the American River between Sunrise Boulevard and River Bend Park. This is the second year the event – whose popularity has evolved briskly via Facebook – is taking place.

Last year, roughly 3,500 people flocked to the river, with law enforcement agencies making 12 arrests and providing aid to nearly 100 people.

“The weather is going to be in the high 90s, and that makes people want to get out on the water and drink,” said Jason Ramos, spokesman for the Sacramento County Sheriff’s Department. “From our standpoint, we have to be prepared.”

The event, which will begin at 11 a.m., is described on Facebook as a day of summer rafting fun for those 21 or older, and will include mud wrestling, cliff jumping, music, homemade grain alcohol and a fruit brew called jungle juice. A river cleanup is slated for Sunday.

It is the alcohol factor that most troubles law enforcement. “We know beyond a shadow of a doubt that we will have problems that come along with alcohol,” said Ramos.

Six law enforcementand rescue agencies will monitor the event.