The head of the UN in Kiribati says the drought situation affecting the country will continue to put more pressure on already water-stressed families and households in the coming months.

On Monday, the Kiribati government declared a nationwide State of Disaster after below-normal rainfall caused high salinity levels in water sources in key monitoring wells.

UNICEF Pacific chief and head of the joint UN presence in Kiribati Nick Rice Chudeau said all 120,000 i-Kiribati had been affected by the drought, after rainfall levels being lowest in the past six months.

Chudeau said the weather and rainfall patterns had become more erratic because of the climate crisis over the past few decades.

He said these kinds of drought events were not new to Kiribati but they had become more frequent, lasted longer and were more intense.

"That is a symptom of the climate crisis that continues to impact already vulnerable communities in Kiribati.

"And the drought outlook is most concerning for islands in the Gilbert group, most notably in South Tarawa and the southern islands of the Gilbert group, over 94,000 people or 79 percent of the total population live on those islands and are therefore at higher risk," he said.