Lava advanced about 85 yards since Tuesday toward Pahoa, Hawaii County Civil Defense officials said Wednesday after a morning overflight.
If it continues at its current pace, the lava could reach Apaa Street on the outskirts of Pahoa in about two weeks and cross Highway 130 in about 28 days, Hawaiian Volcano Observatory scientists said.
The lava is not an immediate threat to homes and no evacuations have been ordered.
However, the state Health Department advised residents who need medical services, treatment or supplies to relocate.
State Department of Health spokeswoman Janice Okubo said lower Puna residents who receive oxygen, dialysis treatment and other recurring health care must consider the possibility that medical services will be limited or cut off if lava crosses Highway 130.
Wednesday’s assessment showed the flow moving along a tree line and burning vegetation producing a significant amount of smoke.
The lava has been moving about 390 feet a day since Oct. 3 and is about a miles upslope of Apaa Street.
The June 27 lava flow started its course toward Hawaii island’s Pahoa town from Kilauea Volcano’s Puu Oo vent in late June. Since Sept. 22 its pace has slowed and, at times, stalled.
The Associated Press contributed to this story.