Geneva, Switzerland's climate is characterized by mild winters and warm summers. January and December are the coldest months, with temperatures ranging from -9°C to 14°C, averaging around 3°C, while May and June mark the beginning of warmer weather, with average highs of 13°C and 20°C respectively. Summer months, July and August, bring pleasant temperatures, often reaching up to 32°C, but with a noticeable drop in September. Autumn and spring periods are generally mild, with April and October experiencing gentle temperature fluctuations around 10-11°C on average.