Clark County has extended a smoke advisory through Thursday because of the haze hanging over the valley from California wildfires.
Smoke is made of small dust particles and other pollutants that can aggravate respiratory diseases and contribute to the formation of ground-level ozone, according to the Clark County Department of Environmental Sustainability.
It may be best for children, the elderly and people with respiratory and heart disease to stay indoors, officials said.
The department suggests limiting outdoor exercise, keep windows and doors closed and change dirty air filters.