The Fijian government's warning the country's 900,000 residents to protect themselves from ashfall almost three days after the huge eruption in Tonga.
The Hunga Tonga-Hunga Haʻapai volcano erupted on Saturday evening, cutting much of the communication network in Tonga and sending tsunami waves and surges around the Pacific.
More than 800 kilometres away in Fiji, people are being advised to cover their water supplies as material from the volcano drifts across the Pacific.
The latest satellite imagery showed a sulphur dioxide cloud moving towards Australia on Tuesday.
Fijians are being told to wear masks when outside, cover their eyes, stay indoors as much as possible, and wear clothing that covers their entire bodies.
Government advice also says to disconnect water tanks if rainwater is being used.
Fiji's environment department said on Monday sulphur dioxide in the atmosphere could result in acidic rainfall over Fiji.
"The Department of Environment is requesting that members of the public cover all household water tanks and stay indoors in the event of rain due to the risk of acid rain," a statement read.
The heavy rain alert over parts of the country has been cancelled, but there is still some heavy rain and thunderstorms on Tuesday, the Fiji Meteorological Service said.
The country's still emerging from the devastating Cyclone Cody, with damage assessments and the recovery effort well underway.