Smoke from wildfires in Australia will drift right around the world and soon return to where it started, NASA says.
The smoke last week reached as far away as South America and had also turned New Zealand's skies bright orange.
"Once in the stratosphere, the smoke can travel thousands of miles from its source, affecting atmospheric conditions globally," NASA said in a statement.
"The smoke is expected to make at least one full circuit around the globe, returning once again to the skies over Australia."
Fires have been raging for months in Australia, and have caused increasing concentrations of carbon monoxide in the country's southeast since September, the European Space Agency said on Saturday.
There had also been an "immense spread" of aerosols from the fires since December 28, the agency said.
Conditions are starting to ease on the fire grounds, with rain forecast for the rest of the week.
"The bushfire regions themselves could see anywhere between 30 and 100mm of rain over those three to four days," said WeatherWatch forecaster Richard Green. "That's the most rain they've had in six months.
"I'd say the heaviest rain at the moment will be on Friday and Saturday," Green told MagicTalk's Brendan Telfer on Wednesday.