Map from Google - Geneva

The climate of Geneva is moderately continental, with cold winters and warm summers. The city is located at 400 metres (1,300 feet) above sea level, on the shores of the lake of the same name. The average temperature of January is 1 °C (34 °F), that of July is 19.5 °C (67 °F).
Here are the average temperatures.
Average temperatures - Geneva
GenevaJanFebMarAprMayJunJulAugSepOctNovDec
GenevaJFMAMJJASOND
Min (°C)-2-11481113131072-1
Max (°C)46101419232625211584
Min (°F)283034394652555550453630
Max (°F)394350576673797770594639

Precipitation amounts to about 950 millimetres (37.5 inches) per year, and is well distributed over the seasons: in the cold half of the year it's due to Atlantic depressions, whereas in summer, when Atlantic depressions become a little rarer, thunderstorms can break out in the afternoon.
Here is the average precipitation.
Average precipitation - Geneva
GenevaJanFebMarAprMayJunJulAugSepOctNovDecYear
GenevaJFMAMJJASONDY
Prec. (mm)808080657590658080759085945
Prec. (in)3.13.13.12.633.52.63.13.133.53.337.2
Days109109111089881010112

Winter, from December to February, is cold: temperatures are often around freezing (0 °C or 32 °F), and there are many gray days. Wind is quite frequent as well, and there are noticeable changes in temperature. In fact the city can be reached by Atlantic depressions, which bring a wet and rainy weather, though relatively mild: in these cases the maximum temperature can reach or exceed 10/12 °C (50/54 °F); but the city can also be reached by cold air masses of Siberian origin, brought by a cold wind from the northeast, the Bise. This wind can make the lake choppy, and sprayed water can freeze, creating an unusual frost on boats, on docks and on the lakefront. Under the influence of the Bise, the temperature may remain below freezing all day, and the wind heightens the feeling of cold, making it seem polar.

Ice near Lake Geneva

The temperature rarely drops below -10 °C (14 °F), for example, in recent years it has dropped to -11 °C (12 °F) in December 2010 and February 2012, but in the past it touched lower values, for example in January 1987 it reached -16 °C (3 °F), in January 1985 -20 °C (-4 °F), in January 1963 -18 °C (0 °F), and in February 1956 -17 °C (1 °F).
Snow can occur during cold air outbreaks, and also later, when the westerlies begin to blow again: in the latter case the snow is going to melt with the passing of hours, when the mild air mass takes over the cold one.

Spring, from March to May, is initially a bit cold, and then gradually becomes milder. In March, snow and frost can still occur, and sometimes also in the first half of April. Typically the temperature becomes pleasant in a more stable manner by the second half of May, when the first afternoon thunderstorms can also erupt.

Summer, from June to August, is quite warm and sunny, though with cool nights, and the breeze blowing from the lake. The Azores High is able to bring periods of good weather, sometimes even long, during which thunderstorms can break out in the afternoon (but less frequently than in other cities of Switzerland). At other times, Atlantic fronts can pass, bringing a bit of rain and cool weather. Very hot days are rare: generally the temperature exceeds 32 °C (90 °F) for a couple of times in a month in July and August (although in the exceptional summer of 2003 the heat lasted for weeks). Sometimes at night it can be even a little cold: the minimum temperature can drop below 10 °C (50 °F) even in July and August.

Autumn, from September to November, is quite rainy; temperatures are initially pleasant, and then become gradually colder. November is usually a cold and dull month.

The amount of sunshine in Geneva is good in summer, when the sun shines quite often, while it is low from November to February, when the sun is rarely seen.

Geneva

When to go

The best time to visit Geneva goes from mid-May to mid-September, being the warmest and sunniest of the year. However, we cannot exclude some rain, or a bit of cool weather, or even cold, especially in May and early June.