Haze from the Kilauea volcano on Hawai'i has been travelled over 6,000 kilometres to reach the Northern Marianas Islands and Guam again.
Lava fountains at "Fissure 8" of Kilauea Volcano on Hawaii's Big Island, June 2018 Photo: U.S Geological Survey
The National Weather Service says the volcanic haze is expected to linger across the region for much of the week.
It says it will decrease periodically due to developing showers but the Easterly tradewinds will continue to funnel the haze towards the Micronesian islands and reduce visibility there.
The service says while the haze is not expected to cause widespread health problems, if people suffer from respiratory health issues then they should limit outdoor activities.
The blue-grey haze first impacted the island in May before dissipating.