SYDNEY — Thick smoke from wildfires has shrouded Sydney and its surrounding areas, with health experts warning residents with medical conditions to remain indoors.

The Sydney skyline was barely visible with air quality in some parts of the city reaching hazardous levels early Tuesday.

Shane Fitzsimmons, the state’s rural fire commissioner, says firefighters would be challenged by high temperatures and wind conditions.

Most of the coastal areas of New South Wales are under very high fire danger with 48 fires burning across the state.

Fires have destroyed 577 homes in New South Wales during the wildfire season, which peaks during the Southern Hemisphere summer but has started early after an unusually warm and dry winter.