The vegetation fires were reported at about 5:45 p.m., according to Cal Fire. The size of the fires was not immediately available.
The No. 2 northbound lane just south of Kastania Road in unincorporated Sonoma County is blocked while fire personnel respond to the scene, CHP Officer Robert Haven said.
Cal Fire has dispatched at least two air tankers to combat the flames, according to a spokesperson.
A Sig-alert was issued at 6:09 p.m.