The Tonga National Emergency Management Office is urging people to prepare for more severe drought, which it says could turn into a crisis in the next month.
Tonga has had extremely dry weather for nearly a year, and three months of low rainfall is expected as a severe El Nino strengthens its grip on the region.
The office's director, Leveni 'Aho, says recent rainfall in Tonga'tapu and Ha'apai has meant the situation is not yet critical for much of the kingdom.
But he says people have to prepare for the worst.
"The main thing for this forecast is to alert, bring awareness, to the general public, that this is the trend that we will anticipate for the rest of the year. So it's for them to take precautions, be careful with rainwater, try to preserve as much, because we might go into a crisis in the next month or so."
Leveni 'Aho says the government is ready to distribute water and use desalination plants if necessary.