Temperature
Temperatures vary a lot by season, location and elevation. Still, Switzerland's climate may be classified as mild. It is strongly influenced by the relatively nearby Atlantic. Winds from the Atlantic transport moist and mild maritime air into Switzerland. This results in a relatively mild climate. On average, the areas north of the Alps are cooler than the areas south of the Alps. South facing slopes receive more sunshine and are warmer than north facing slopes. Wide valleys and lakes receive more sunshine than narrow valleys. Elevation is what influences the temperature most. Every 100 m (328 ft) of gaining height causes temperature drops up to 1 °C (1.8 F). On mountain tops it may be chilly even in Summer and you may encounter thick layers of snow. In low sunny areas like Lake Geneva and the Rhône valley in the Valais, there is a Mediterranean climate in summer. Palm trees can be found in the sunniest region of Switzerland: the Lago Maggiore in Ticino.
Warmest months: July and August;
Warmest areas: Lake Geneva, the Rhône valley up to Brig, and the valleys of Ticino. All low elevation areas around lakes and rivers from the West to the North East (Geneva - Zurich - St. Gallen) are pretty warm as well;
Coolest months: January and February;
Coolest areas: all places high up in the mountains and the Engadine.