Mount Ruapehu is heating up -- but there's no need to panic, a volcanologist says.
Ruapehu's Crater Lake has reached 40degC, the third-highest temperature recorded at the lake since 2002.
Other signs, including gas output, minor seismic activity and changes in lake chemistry were also typical of a volcano in a heating cycle, GeoNet vulcanologist Tony Hurst said.
Ruapehu entered its current heating cycle last October, the eighth since the lake was re-established in 2002 after the 1995-1996 eruptions.
Ruapehu is on volcanic alert level one, which indicates signs of volcano unrest, but Mr Hurst told NZPA that was normal for an active volcano such as Ruapehu.
The colour of the lake might change and steam might be seen wafting off it if sediments on the lake floor were disturbed by increasing gas and heat flows into the lake, he said.
Scientists would continue to monitor the situation.
At 2797m, Ruapehu is the highest mountain in the North Island, and the most recent of the North Island volcanoes to have erupted.
GeoNet is a collaboration between the Earthquake Commission and GNS Science.