Volcanic tremors have been detected beneath Mt Ruapehu and the crater lake's temperature continues to creep up.
But there has been no need to lift the alert level, GeoNet says.
The tremors and small earthquakes have been occurring beneath the volcano since Friday, and are common during a heating phase of the lake.
Mt Ruapehu's Crater Lake Te Wai ā-moe became re-established in 2003 after the 1995/1996 eruption. It is now going through a regular phase of heating, which volcanic tremors and small earthquakes are characteristics of.
During this heating phase, the colour of the lake changes from pale blue to grey, and right now it's a grey tone.
But these changes are normal, according to GeoNet, and there has been no need to lift the alert level. It remains at volcanic alert level 1, which indicates minor volcanic unrest, and the Aviation Colour Code is at Green.
"The lake temperature reached a relative low of 22degC on 11 August and started to rise a few days later," GeoNet said in a statement.
"The heating has continued and the lake's temperature has risen to around 30degC and the lake is overflowing. This is expected activity for the Crater Lake."
The lake has undergone 15 heating-cooling cycles since 2003, and no eruptions have occurred, so there's no reason for alarm.
Two small eruptions in 2003 originated from a cooler lake.
Newshub.
