weather in early oct

Guidebooks including Rick Steve's books typically have climate charts/data on a month by month format with temperature, precipitation and even number of sunny or dry days

You can also do internet searches for "climate" and country to find data sources such as:
http://www.studyinginswitzerland.ch/country-climate.htm
http://www.myswitzerland.com/en-us/climate.html

Recognizing that weather depends on place and elevation you can use the Norwegian weather suite to check weather statistics for specific cities like Zermatt:
And Zurich:
http://www.yr.no/place/Switzerland/Valais/Zermatt/statistics.html
http://www.yr.no/place/Switzerland/Zürich/Zurich/statistics.html

Weather in Switzerland depends (in addition to time of year) on whether you're in the mountains or down at a lower elevation.

Follow up discussion to weather being "place and elevation" dependant.

Mountains affect localized weather. It'd called the "mountain effect" where the upwelling of air influences localized and beyond weather. See:
http://www.mountainprofessor.com/mountain-environment.html

Elevation affect temperature. All things equal, temperature drops with elevation. Rough rule of thumb is air temp drops 3° to 5° F for every 1000 feet or 6° to 10° C for every 1000 meters of climb. See:
http://www.onthesnow.com/news/a/15157/ask-a-weatherman--how-does-elevation-affect-temperature-

At least Switzerland being somewhat inland is away from marine influences.

The temperature forecast difference between Zermatt base elevation of 1620 masl vs a mid mountain 3883 masl (T base vs T top) illustrates the effect of elevation:
http://www.meteoexploration.com/forecasts/Zermatt/
And note that the real top of the Matterhorn is about 4478 masl.