The temperature of Mt Ruapehu's Crater Lake/Te Wai ā-Moe has risen to 32C, but it's no reason to panic, scientists say.
Volcanologists from GNS Science say the temperature of the lake has been rising since early December, "remaining hot".
However, all its monitoring indicators are still within normal ranges, despite peaking at 35.5C on December 27.
GNS is keeping the alert level at 1 due to continuing weak volcanic tremors, combined with their latest water chemistry, gas, and temperature data.
Alert levels reflect how much volcanic unrest there is currently - level 1 means minor unrest while level 5 means a major eruption.
At its current temperature, GNS said it's "consistent with heat flow into the lake of about 150-200 megawatts".
In April and May last year, Mt Ruapehu experienced its longest period of strong tremors in over 20 years, where the temperature peaked at 41C for 12 days.
Volcanic tremors increased slightly around mid-December but have been weak since.
"Mt Ruapehu is an active volcano and has the potential to erupt with little or no warning when in a state of minor volcanic unrest," a GNS spokesperson said.
GNS is continuing to monitor Ruapehu for any changes.
