The National Gallery of Australia has closed to protect the public, staff and works of art.

The National Portrait Gallery, National Film and Sound Archive, High Court and many pools have closed as well.

Many businesses have closed, even those within shopping centres.

The War Memorial and National Museum have remained open.

Canberra once again has the worst air quality index of any major city in the world, coming in worse than Sarajevo in Bosnia Herzegovina, Lahore in Pakistan and Delhi in India.

The air quality index at Civic measured 2843 at midday, Monash measured 1655 and Florey 3153. A reading 200 is considered hazardous.

The orange-tinged smoke has made breathing outside very difficult. It has entered homes and offices buildings across the capital. Residents reported light, patchy rain in the early morning.

By 2pm, Canberra had reached 20 degrees, with a forecast top of 24 degrees.

Southeasterly winds will becoming easterly in the late afternoon, meaning there will be no respite from the smoke.

The Bureau of Meteorology says the smoke is likely to be at its thickest in the morning and evening, and it's forecast to remain for coming days.

The bureau issued a road weather alert for Canberra for Sunday morning, as reduced visibility due to smoke made driving conditions dangerous.

The heavy smoke is expected to stay with us for the coming days, the ACT Emergency Services Agency has advised.

The fire danger rating in the ACT for Sunday is high and a total fire ban has been declared. A State of Alert remains in place for the ACT.

The agency said the orange light was caused by sunlight coming through heavy smoke particles and the colour would fade as the sun rose higher in the sky. They sky soon turned grey.

There were no bushfires in the ACT as of 2pm. But ACT Fire and Rescue responded to more than 200 automatic fire alarms on Saturday night that were triggered by the thick smoke.

READ MORE:

Common reactions people may experience with heavy smoke include: itchy or burning eyes, throat irritation, runny nose, and coughing.

Advice from ACT Health advice remains to avoid exposure to the smoke by staying indoors where possible and not using evaporative air conditioners, which draw air into the house from outside. P2 and N95 masks do filter some smoke but need to be fitted accurately to ensure their effectiveness.

Emergency services responded to a car fire in Coane Street, Holder about 5am on Sunday. The fire was extinguished.

ACT firefighters were called to two small grass fires on Saturday night, one on Kent Street in Deakin and the other near the Woden Cemetery.

Both fires were extinguished quickly and crews are no longer on scene, an ESA spokesperson said. The causes will be investigated.

Many nature reserves and roads in the ACT will remain closed until 11:59pm on Monday, January 6, ACT Parks and Conservation executive branch manager Justin Foley said in a statement.

"For safety reasons due to excessive smoke and high fire dangers I have made the decision to maintain the closure of our managed estate west of the Murrumbidgee River, Kowen Forest, the Mulligans Flat Sanctuary and Googong Foreshores," he said.

The following reserves are closed:

Five campgrounds remain closed for the entire fire season. These are:

Additionally, the following roads in northern Namadgi National Park are closed for the entire fire season: