In general, Slovenia is temperate with four distinct seasons, but the topography creates three individual climates. The northwest has an alpine climate with strong influences from the Atlantic and abundant precipitation. Temperatures in the alpine valleys are moderate in summer but cold in winter. The coast and a large part of Primorska as far as the Soča Valley has a Mediterranean climate with warm, sunny weather much of the year, and mostly mild winters (although the burja, a cold and dry northeasterly wind, can be fierce at times). Most of eastern Slovenia has a Continental climate with hot (and occasionally very hot) summers and cold winters.
Slovenia gets most of its rain in the late spring (May and June) and autumn (October and November); precipitation varies but averages about 900mm in the east, 1300mm to 1600mm in the centre (Ljubljana), 1100mm to 1300mm on the coast and up to 3500mm in the Alps. January is the coldest month, with an average annual temperature of -2°C, and July is the warmest (19°C to 23°C). The mean average temperature is around 10°C in Ljubljana, 7°C in the mountains and 13.5°C on the coast. The number of hours of sunshine per year ranges from 1500 to 2300, with Ljubljana at the low end of the scale and Portorož at the top.
When to go
Every season has its attractions in Slovenia. Snow can linger in the mountains until late June and even July, but spring is a great time to be in the lowlands and flower-carpeted valleys (though it can be pretty wet in May and June). At the same time the days are getting longer, the theatres and other cultural venues are in full swing, off-season rates still generally apply and local people are not yet jaded by waves of summertime visitors.
Summer (mid-June to sometime in September) is the ideal time for hiking and camping, but it’s also the peak season for visitors, making accommodation (and a restaurant table) in Ljubljana and on the coast hard to come by without advance booking. September can be an excellent month, with plentiful local fruit and vegetables, shoulder-season tariffs in effect again and the tourist masses home and back at work. You can still swim comfortably in the Adriatic in September, but by mid-October most of the camping grounds have closed down and the days are growing shorter. Autumn is beautiful, particularly in the mountains of Gorenjska and Štajerska, and it’s the best time for hiking and climbing (though October and November can be rainy).
Winter (December to March) in Slovenia is for skiers. It can be very cold and, away from the mountains, often quite bleak. At the same time, winter sees museums and other tourist sights closed or their hours sharply curtailed. Skiers should bear in mind that Slovenian school kids have winter holidays for about 10 days between Christmas and just into the New Year and again for a week in the second half of February.