The four-alarm blaze sent thick plumes of smoke into the air and triggered evacuations for neighborhoods close to the park.
Those evacuations were lifted within hours as firefighters brought the flames under control, sparing homes from damage.
The blaze was initially reported at 12:49 p.m. By 4 p.m. firefighters said the forward progress was stopped and they were building containment lines and mopping up hotspots.
A care and reception center for local residents had been established at Bobby Bonds Park Cesar Chavez Community Center, at 2060 University Ave.
Road closures were expected to remain in place at least through the early evening, including Central Avenue from Canyon Crest Drive to Fair Isle Drive and Lochmoor Drive from Central Avenue to Fair Isle.
TRAFFIC ALERT: Sycamore Canyon Wilderness Park Area— Riverside Police (@RiversidePolice) July 2, 2019
Due to a vegetation fire in the Sycamore Canyon Wilderness Park the following roads will be closed to ALL TRAFFIC.
• Central Ave. from Canyon Crest Dr. to Lochmoor Dr.
• Lochmoor Dr. from Central Ave. to Fair Isle Dr.