The city has a subtropical Mediterranean climate, with sunny dry summers and very mild rainy winters. During the period between April and October, clear-sky weather is almost an everyday feature. The atmosphere is always warm, but fierce heat waves (temperatures above 38°C) are not very common, since the prevailing Etesian winds (“Meltemia”) blow from northern directions and pleasantly moderate the conditions. Intervals of sunny days are frequent during the windy and rainy winter as well. Snow and frost are rare near the coast, with very few exceptions, like the snowstorm on 13 February 2004, when 25–75 cm (9.8–29.5 in) of snow accumulated in the urban area. The last significant snowstorm happened in 8 January 2017 when the whole city and the old harbor were blanketed by snow. However, such cold days can be followed by much warmer and sunny weather.
For further info: http://www.meteo.gr/cf.cfm?city_id=21