During the summer in the Alps (June – September) we experience usually fair and quite warm weather. It is often sunny and the temperatures can reach 30° Celsius, although it is a dry heat. The weather in the mountains can be sometimes quite unpredictable and weather situations can change very quickly. Therefore, it is necessary to be always prepared for such a change. Another fact is that you will be hiking in different altitude levels so there will be a significant change between the valley ground and the high mountain passes. On a rainy day temperatures can drop quite low and it is necessary to have a good rain jacket and sometimes even a hat and a pair of gloves.
Risks & Hazards
Inclement weather such Thunderstorms, flash floods, fog, snow and other meteorological events may or may not be predictable, and may require immediate response for safety. Lightning is a frequent and serious threat in many regions on the TMB, especially in the late afternoon / early evening on hot days in July and August.
How to get informed
On the Tour du Mont Blanc you hike through 3 different countries (France, Italy, Switzerland). That means that you have many different sources where to get your weather data / forecast from. The Mont Blanc massif can be tricky. Whilst it can be rainy and stormy on one side of the massif it can be the complete opposite on the other side. Here a few links where you can get reliable data from:
France: Chamonix – Meteo
Switzerland: Meteo Swiss