Volcanic haze from Hawaii's Kilauea volcano has now reached the Northern Marianas and Guam, over 6,000 kilometres away.
Haze of Tumuning, Guam Photo: NWS Facebook
The blue-grey haze which initially covered the Marshall Islands, reached the Northern Marianas and Guam over the past few days.
The weather service's Clint Simpson said people with respiratory health problems should monitor outdoor conditions.
Mr Simpson said mariners and pilots have also been warned to be aware of the slightly lower visibility.
"They just need to be aware of it and if you are a visible flight rules pilot you need to be very aware that you will not have good visibility and if you are a sailor you realise that if you get more than five miles away from shore or something you will not be able to see your way back to the island," he said.
"You will have to navigate your way back to the island."
A satellite image provided by the National Weather Service Guam shows volcanic haze moving toward the Mariana Islands and Micronesia region. Photo: National Weather Service Guam/ Guam Daily Post
Satellite imagery showed a dense plume of haze spanning the central Pacific that becomes more diffused closer to the Marianas.
The haze is being carried along by the east-northeast trade winds.
Mr Simpson said the situation would improve in most areas over the next few days, barring any new eruptions in Hawaii.
He said whenever there was volcanic activity in Hawaii the islands of Micronesia would often be impacted in a similar way within 10 days.
Rain that is forecast for the Marshall Islands and later for the other islands, is expected to help dissipate the haze.
The National Weather Service said residents should continue to monitor information from their service as well as the local emergency management offices.