Patchy morning fog and smoke from several hazard reduction burns crackling around the city created a haze which hung around well into the morning, causing widespread visibility issues.

Air Services Australia said the fog and smoke was to blame for delays to inbound and outbound flights at the airport.

They advised passengers to check with their airline for more information.

ACT Policing said they weren't aware of any crashes caused by the lingering smog but advised drivers to exercise caution.

Rob Taggart from the Bureau of Meteorology said he expected the haze to hang around into the afternoon, but it should dissipate as the temperature rises.

He said clear skies coupled with cooling temperatures has sealed the smog over the city.

"There's been some hazard reduction burns around Black Mountain and in terms of how the atmosphere is it's very clear skies, so it's allowed the conditions to cool quite well overnight," Mr Taggart said.

"That means you've got very cool air close to the surface and warmer air aloft and that basically traps the smoke, it can't escape from the lower parts of the atmosphere and that's what creates those smoggy conditions," he said.

The burns have also made for more favourable fog conditions, Mr Taggart added.

"When there's fires in the vicinity, that puts extra particles in the atmosphere and that increases the likelihood of fog forming, because water droplets can form on the particles in the atmosphere," he said.

But cloud coming in from the west should stop the smoke and fog from sticking around on Thursday, even if there are patches in the morning.

There should be less smoke around too with hazard reduction burns scheduled to wind up over the next few days.

A burn of over 230 hectares of piles of logs and pine debris at the Kowen Pine Forest will finish on Thursday, while a 23-hectare burn at Black Mountain Nature Reserve will wrap up on Wednesday.

A third place was also due to take place at Aranda from Wednesday.

People are urged not to call triple-0 for these fires but to report any other new fires which are unattended by firefighters.

Nearby residents with asthma, other chronic respiratory or cardiac diseases should not perform vigorous exercise and should stay inside if affected by the smoke.

Those affected by asthma should continue their medication and consult their general practitioner if they have any difficulties.