Ruapehu volcano (North Island, New Zealand) - Smithsonian / USGS Weekly Volcanic Activity Report for 6 June-12 June 2018 (New Activity / Unrest)

On 5 June GeoNet reported that a new heating cycle at Ruapehu's summit Crater Lake began, as indicated by a recent rise in the water temperature. The increasing lake temperature began 29 May, at a rate of about 1°C per day. Volcanic tremor also increased, representing a greater flow of hydrothermal fluids into the lake.
Many heating and cooling cycles have occurred in the past; the current cycle does not indicate an unusual sign of unrest. The Volcanic Alert Level remained at 1 (minor volcanic unrest) and the Aviation Color Code remained at Green.

Source: GeoNet
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From: Global Volcanism Program, 2018. Report on Ruapehu. In: Mayberry, G (ed.), Weekly Volcanic Activity Report 6 June-12 June 2018. Smithsonian Institution and US Geological Survey.