快晴の山頂へ軽快な登高 午後風に注意

The summit of Ontake-san currently enjoys clear skies with a temperature of 2.4°C, feeling like -0.6°C due to minimal wind. Conditions will remain mostly clear throughout the day, with temperatures rising to 7.8°C by noon. This provides a comfortable window for ascent from routes such as Kurozawa-guchi or Otaki-guchi towards Kengamine, particularly in the morning. The ground is dry with no snow cover, making crampons unnecessary, but caution is advised on the exposed white volcanic scree slopes above the treeline due to loose rocks.

Despite the rising temperatures, the summit's wind chill will remain near freezing. Around 3 PM, northwesterly gusts up to 8.7 m/s are forecast, which will significantly lower the perceived temperature. Proper layering is crucial: a wicking base layer, an insulating mid-layer (fleece or light down), and a windproof outer shell are essential. Always carry a helmet as recommended for this active volcano. Temperatures will drop sharply after sunset, reaching below freezing by midnight, making a strict adherence to daylight hours for your ascent and descent mandatory. Monitor for any signs of volcanic gas, and descend immediately if an unusual odor is detected.