July and August are the months to swim in the lake, dive off jetties, discover the city’s alfresco cafe society and picnic in its many parks.
Winter, with its December festivals, toasty lakeside sauna bars and fondue cuisine (not to mention nearby skiing) is a real charmer.
Read more: http://www.lonelyplanet.com/switzerland/geneva/essential-information#ixzz4CrSNW75x