Places in the Alps by sunshine duration

CAUTION: Please note the maps below show solar power (kWh/m2), which exactly is not what I was looking for, because it depends on geographic location (latitude) - the more to the south you go, the more energy you get from the sun for the same amount of sunshine. Hence, values only in a relatively small area can be compared.

During my search I found some maps for the photovoltaic industry that show the Alpine region:

• Global irradiation and solar electricity potential

• Yearly total of global horizontal irradiation, Alpine region

Both these are by Photovoltaic Geographical Information System (PVGIS) where you can also find more detailed maps (usually by country) if you want.

Also, if you live in Europe and want to compare your home location do a desired destination in the Alps, you can use one of these maps that show whole Europe:

• Solar Radiation Map of Europe: Global Horizontal Irradiance Map of Europe (SolarGIS 2011)

• Photovoltaic Solar Electricity Potential in European Countries (PVGIS 2012): standard resolution (0.8 MB), high resolution (4.9 MB). In case links are dead see homepage.

From what I see in the maps probably the best location regardless elevation is French Alps and southwestern Italy or one has to climb high enough above the clouds pretty much anywhere.

Other answers focus on the total power of sunshine on a yearly or monthly basis. Since you're in for outside activities and not for generating electricity from the Sun, I think that as a tourist, the total number of hours of sunshine on a monthly basis more relevant. For Switzerland, Meteoswiss records such figures. The map below is for the entire year:

^{Source: Meteoswiss}

In data, you can find sunshine in hours and sunshine in percent directly from the Swiss climate table page.

The tables have the distinct advantage that they record information per month. The sunniest location certainly depends on the season, so if you find a year-based map you may end up quite disappointed!

Other national institutes may record similar data, but there is no unified data source, so you would have to check it per country.

What Relaxed said; no way can you guarantee in advance. I spent last June through September in Switzerland, whose north had a lousy summer, especially July. But the Graubunden lived up to its reputation as being sunnier than elsewhere, and I enjoyed some very good weather after I had abandoned the incessant drizzle of the Oberland for Zermatt. OTOH when I returned from Zermatt to the Oberland, I found new snow (in August!) at the same altitude where I had previously enjoyed flowering meadows.

In the Alps you can really improve your weather by a shortish train ride. My advice would be to stay south of the Rhine-Rhone watershed, or be prepared to move there sharpish.