The National Weather Service in Reno issued a Dense Smoke Advisory Monday for an area stretching from north of Reno to south of Gardnerville and throughout Lake Tahoe and Truckee through 8 p.m. Monday.
The Dense Smoke Advisory will resume Tuesday from 11 a.m. to 8 p.m.
But National Weather Service forecasters don't expect the air to improve much through Wednesday. Reno's air is considered unhealthy for the elderly, young children and people with respiratory problems.
The most unhealthy air quality levels have been where the fire is burning, in El Dorado and Placer counties. But as winds shift, so does the smoke. The air quality where the fire started has improved over the past week.
"In Camino and Pollock Pines today [Monday] the levels are down in the good range, zero to 50, whereas last week they were up over 500 to a thousand in the hazardous range," said Dave Johnston, with the El Dorado County Air Quality Control District.
He said dust masks, "N-95 or P-100 rated," can provide protection from fine particulate matter, which is the major pollutant in wildfire smoke.
The Placer County Air Pollution Control District Monday recommended closure of schools in the Colfax and Foresthill areas due to hazardous levels of fine particulate matter.
The District also advised people to avoid outdoor activity in Squaw Valley, Truckee and Auburn.
Officials said Monday the smoky conditions are expected to continue from Placer County to the Lake Tahoe area, depending upon wind direction, until the King Fire is completely out.
The National Weather Service in Reno forecast said visibility could drop to near one mile at times, "especially during the afternoon and evening, when smoke from the King Fire is most likely to spread east of the Sierra Crest."
The forecast also said periods of dense smoke from the fire could create low visibility on I-80, Highway 50 and Highway 89.
The Sacramento NWS issued a Fire Weather Watch for Wednesday. The forecast covers northeast California and northwestern Nevada, including northern Washoe County. The forecast is for gusty winds and 10-15 percent humidity.