Sulphur dioxide emitted from the Hunga Tonga-Hunga Ha'apai volcano continues to spread over the Ha'apai, Vava'u and Niuatoutapu groups drifting NNE at a high altitude of 8-14km.

Tonga Geological Service reported today, “SO2 detected over Ha‘apai, Niuatoputapu and Vava‘u Group. It measured highest near the ‘Otumu‘omu‘a Group.”

If it rains, they warned yesterday that the dust from the eruption and the gas can contaminate water tanks. “It can result in a slightly acidic rainfall (pH2.5-5.0). The acid will typically be dominated by hydrochloric acid and sulfuric acid arising from plume gases and sulphur dioxide.”

They advised all Tongans to disconnect their water tanks until the eruption ceases. Symptoms of exposure to acid rain are itchiness and skin irritation, blurry and discoloration of vision if exposed to the eye. 
It may cause water to taste acidic

This morning, 23 Dec., TGS said the steam cloud formation from the eruption had reduced significantly from yesterday.

Meanwhile, the gaseous white cloud column from the volcano formed an impressive sight on the horizon seen from Nuku'alofa today, after a spectacular lightning display last night.

“The gaseous emission caused a build up of a cumulonimbus cloud in the eruption region resulting in spectacular lighting throughout the evening and night,” said TGS.

The Hunga Tonga-Hunga Ha'apai volcano is 65 km from Nuku'alofa.