現在の赤岳山頂はほぼ晴れ、体感10.6℃と比較的穏やか。山麓との気温差は約8.4℃。日中は快晴が続き、山頂気温は17℃台まで上昇する見込み。風も弱く、行動しやすい一日となる。
地面はドライな岩稜露出状態。しかし、八ヶ岳の岩稜帯は文三郎尾根や地蔵尾根の鎖場を擁し、視界不良や濡れた岩場での滑落リスクが高い。現在の視程は2.4kmとやや短いが、日中は回復傾向。夏山特有の局地的なガス発生による濃霧には常に警戒し、視界不良時は無理な行動を控えること。
標高2893mでの体感気温は日中17℃台となるが、行動中の発汗と停滞時の冷え込みを考慮し、ベースレイヤーに速乾性、ミッドレイヤーに薄手フリース、アウターに防風防水シェルを基本とする。予報では雷・強風のリスクは低いが、雨具は携行する。夜間は10℃台まで冷え込むため、宿泊者は十分な防寒着を用意すること。
長野県・山梨県
八ヶ岳（赤岳）
Yatsugatake (Mt. Aka)
2026年7月15日 06:57 更新
夏日差しの岩稜帯。稜線は視界に注意
Stable Weather for Rock Ridge Traverse. Mind Localized Fog and Visibility.
現在の気象状況 — Current Conditions
▲ 山頂エリア (Summit)
気温 Temp
+12.2°C
風速 Wind
1.9m/s
W
天候 Weather
🌤️ ほぼ晴れ
体感 Feels Like
+10.6°C
▼ 登山口・山麓エリア (Base)
気温 Temp
+20.6°C
風速 Wind
1.6m/s
NW
天候 Weather
🌤️ ほぼ晴れ
標高 Altitude
1,492m
山頂の3時間予報 — Summit Forecast
09:00
+14°C
1.9m/s
W
💧 0mm
(0%)
12:00
+17°C
2.4m/s
WSW
💧 0mm
(0%)
15:00
+18°C
2.6m/s
WSW
💧 0mm
(2%)
18:00
+14°C
2.3m/s
WSW
💧 0mm
(18%)
21:00
+12°C
2.3m/s
WSW
💧 0mm
(12%)
00:00
+11°C
2.9m/s
WSW
💧 0mm
(2%)
03:00
+11°C
2.9m/s
W
💧 0mm
(2%)
気象分析 — Analysis Report
日本語
コンディション概ね良好 — 通常の山岳安全対策を実施すること
English
Conditions generally good — Conduct standard mountain safety measures
Current conditions at Mt. Akadake summit are mostly clear with a comfortable felt temperature of 10.6°C. The temperature difference from the base is approximately 8.4°C. The forecast indicates clear skies throughout the day, with summit temperatures rising to the upper 17s. Winds will remain light, making for a pleasant day for climbing.
Ground conditions are dry on the exposed rocky ridges. However, the Yatsugatake mountain range, particularly the rocky sections such as Bunzaburo-one and Jizo-one with their chains, present a heightened risk of slipping if the rock is wet or visibility is poor due to fog. Current visibility at 2.4km is somewhat limited but expected to improve during the day. Always be vigilant for localized fog, a common summer mountain phenomenon, and avoid pushing forward if visibility deteriorates.
For climbing at 2893m, with felt temperatures reaching the upper 17s during the day, a layering system of quick-drying base, thin fleece mid-layer, and a windproof/waterproof shell is recommended to manage perspiration and prevent chilling during stops. Although the forecast shows a low risk of thunderstorms and strong winds, carrying full rain gear is essential. Overnight temperatures will drop to around 10°C, so those planning overnight stays must prepare adequate warm clothing.
Ground conditions are dry on the exposed rocky ridges. However, the Yatsugatake mountain range, particularly the rocky sections such as Bunzaburo-one and Jizo-one with their chains, present a heightened risk of slipping if the rock is wet or visibility is poor due to fog. Current visibility at 2.4km is somewhat limited but expected to improve during the day. Always be vigilant for localized fog, a common summer mountain phenomenon, and avoid pushing forward if visibility deteriorates.
For climbing at 2893m, with felt temperatures reaching the upper 17s during the day, a layering system of quick-drying base, thin fleece mid-layer, and a windproof/waterproof shell is recommended to manage perspiration and prevent chilling during stops. Although the forecast shows a low risk of thunderstorms and strong winds, carrying full rain gear is essential. Overnight temperatures will drop to around 10°C, so those planning overnight stays must prepare adequate warm clothing.
山岳ガイド — Mountain Guide
概要 Overview
長野県と山梨県にまたがる八ヶ岳連峰の最高峰、赤岳の標高は2,899m。南八ヶ岳の険峻な岩稜帯と北八ヶ岳の穏やかな樹林帯という対照的な山容を併せ持ち、四季を通じて登山者に親しまれる。
特徴・地形 Features
赤岳・横岳・硫黄岳と続く主稜線は鎖場・梯子・痩せ尾根が連続する岩稜帯。針葉樹林、苔の森、お花畑など多様な植生も魅力。冬期も山小屋営業があり通年登山可能。
ベストシーズン Best Season
6月〜10月が一般シーズン。冬期登山も人気だが、稜線の強風と凍結への対応が必須。シャクナゲは6月下旬。
主要ルート Main Routes
美濃戸口起点行者小屋経由（最一般的）、赤岳鉱泉経由、真教寺尾根、県界尾根、横岳〜硫黄岳縦走。
注意点・危険箇所 Cautions
文三郎尾根・地蔵尾根の鎖場で滑落事故が多発。冬期は強風による転倒・凍傷に注意。雷雨時の稜線行動は危険。
アクセス Access
中央自動車道諏訪南ICから美濃戸口へ。中央線茅野駅からバス便。
※ 本ガイド情報は一般的な参考資料であり、最新の登山道状況・規制情報は各自治体・登山口の公式情報をご確認ください。