Located on the watershed between the Rhône and the Po, the Mont Blanc massif is also situated between the two different climatic regions of the northern and western Alps and that of the southern Alps.
Climatic conditions on the Mer de Glace are similar to those found on the northern side of the Swiss Alps.

The climate of the Mont Blanc massif is cold and temperate (Köppen climate classification Cfb), and is greatly influenced by altitude.
The main valley settlements around the perimeter of the massif are at an altitude ranging between 600 and 1,200 metres (2,000 and 3,900 ft).
Daytime valley temperatures in July and August may range up to 25 °C (77 °F), sometimes reaching 30 °C (86 °F).
The greatest snowfall occurs between the months of November and April.

The best weather for mountaineering or hiking occurs between late June to early October but, being the highest part of the Alps, the Mont Blanc massif can create its own weather patterns.
Temperatures drop as the mountains gain in height, and the summit of Mont Blanc is a permanent ice cap, with temperatures around −20 °C (−4 °F).
The summit is also prone to strong winds and sudden weather changes.
Because of the massif's great overall height, a considerable proportion is permanently glaciated or snow-covered and is exposed to extremely cold conditions.
Even on the high passes of the Tour du Mont Blanc, around 2,000 to 2,500 m (6,600 to 8,200 ft), summer temperatures can be between 5 and 15 °C (41 and 59 °F), but feeling much colder because of wind chill in windy or wet conditions.

Precipitation is distributed fairly evenly over all months of the year, and mostly originates from a westerly airflow.
There is, however, significant variation in precipitation with altitude.
For example, Chamonix has an elevation of approximately 1,030 metres (3,380 ft) and receives around 1,020 mm (40 in) of annual precipitation, whilst the Col du Midi, which is at 3,500 metres (11,500 ft) above sea level, receives significantly more, totalling 3,100 mm (122 in).
However, at an even higher altitude (near to the summit of Mont Blanc) precipitation is considerably less, with only around 1,100 mm (43 in) recorded, despite the latter measurements being taken at a height of 4,300 metres (14,100 ft).

In the mountains further south of the Mont Blanc range, annual precipitation is significantly less than at equivalent altitudes within the massif.
For example, the valleys in the Pelvoux massif at around 1,000 metres (3,300 ft) receive only around 600 to 700 mm (24 to 28 in) of precipitation per year, which is significantly less than that in either Courmayeur or Chamonix.
Located on the watershed between the Rhône and the Po, the Mont Blanc massif is also situated between the two different climatic regions of the northern and western Alps and that of the southern Alps. Climatic conditions on the Mer de Glace are similar to those found on the northern side of the Swiss Alps.
The climate of the Mont Blanc massif is cold and temperate (Köppen climate classification Cfb), and is greatly influenced by altitude. The main valley settlements around the perimeter of the massif are at an altitude ranging between 600 and 1,200 metres (2,000 and 3,900 ft). Daytime valley temperatures in July and August may range up to 25 °C (77 °F), sometimes reaching 30 °C (86 °F). The greatest snowfall occurs between the months of November and April.
The best weather for mountaineering or hiking occurs between late June to early October but, being the highest part of the Alps, the Mont Blanc massif can create its own weather patterns. Temperatures drop as the mountains gain in height, and the summit of Mont Blanc is a permanent ice cap, with temperatures around −20 °C (−4 °F). The summit is also prone to strong winds and sudden weather changes. Because of the massif's great overall height, a considerable proportion is permanently glaciated or snow-covered and is exposed to extremely cold conditions. Even on the high passes of the Tour du Mont Blanc, around 2,000 to 2,500 m (6,600 to 8,200 ft), summer temperatures can be between 5 and 15 °C (41 and 59 °F), but feeling much colder because of wind chill in windy or wet conditions.
Precipitation is distributed fairly evenly over all months of the year, and mostly originates from a westerly airflow. There is, however, significant variation in precipitation with altitude. For example, Chamonix has an elevation of approximately 1,030 metres (3,380 ft) and receives around 1,020 mm (40 in) of annual precipitation, whilst the Col du Midi, which is at 3,500 metres (11,500 ft) above sea level, receives significantly more, totalling 3,100 mm (122 in). However, at an even higher altitude (near to the summit of Mont Blanc) precipitation is considerably less, with only around 1,100 mm (43 in) recorded, despite the latter measurements being taken at a height of 4,300 metres (14,100 ft).
In the mountains further south of the Mont Blanc range, annual precipitation is significantly less than at equivalent altitudes within the massif. For example, the valleys in the Pelvoux massif at around 1,000 metres (3,300 ft) receive only around 600 to 700 mm (24 to 28 in) of precipitation per year, which is significantly less than that in either Courmayeur or Chamonix.
Mont Blanc massif