In Slovenia, there is a clear separation between the western flat area, stretched from Nova Gorica to northern Istria, which has a quite mild climate, and the interior, which has a moderately continental climate (in the hills, the valley bottoms and the eastern plain) or a cold mountain climate (in the mountains).
Precipitation is abundant in the western part of the country, where it ranges between 1,000 and 1,500 millimeters (40 and 60 inches) per year in plains and hills, while it exceeds 2,000 mm (80 in) in the mountains, and even 3,000 mm (120 in) on the most exposed slopes. Only in plains and hills of the far east, precipitation is less abundant, and decreases below 900 mm (35.5 in).

Index


The western plain



About 30 kilometers (18 miles) away from the coast, there is a mountain range that separates the interior from the sea, so the western plains of Slovenia that are influenced by the sea are not vast. This flat area close to the coast has a climate that can be described as transitional Mediterranean. In fact, winter is quite mild in cities such as Portorož, Piran, Izola, Koper, though you cannot fully define it as Mediterranean, since the average temperature in January is around 5/6 °C (41/43 °F).

Piran

In addition, this area is exposed to a fearful wind: the temperature undergoes sudden drops when the Bora makes its appearance, that is, a cold and furious wind which blows more often in the cold half of the year and which can be accompanied by clear skies (light Bora) or more rarely by cloudy skies, with rain or snow (dark Bora). Since the Bora comes from the plains of Eastern Europe, it is usually dry, so, snowfall in this area is rare and usually not abundant.
Summer in the western plain is warm or even hot, averaging around 23 °C (73 °F) in July and August, though it's tempered by the breeze. The rains are frequent throughout the year, with a maximum in autumn (September to November), a relative minimum in winter, and an increase between late spring and summer. This is not to say that summer is a bad season, but you have to take into account some thunderstorms in the afternoon, and even a few days when Atlantic disturbances manage to move over the country, maybe accompanied with some cool gusts of Bora.

Portoroz

Here are the average temperatures of Portorož, located on the coast of the northern Adriatic Sea, on the Gulf of Trieste.
Portoroz - Average temperatures
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Min (°C)336913161919161274
Max (°C)681115192326262218128
Min (°F)373743485561666661544539
Max (°F)434652596673797972645446

Rainfall in Portorož is fairly abundant, around 1,000 millimeters (40 inches) per year, and it's well distributed throughout the year, in fact, there can be some rain even in summer, often in the form of thunderstorms. However, the rainiest season is autumn. Here is the average rainfall.
Portoroz - Average precipitation
MonthJanFebMarAprMayJunJulAugSepOctNovDecYear
Prec.(mm)65607080851007590110125105801045
Prec.(in)2.62.42.83.13.33.933.54.34.94.13.141.1
Days9881411109911121411126

In Portoroz and along the Adriatic Coast, the sun does not shine very often in winter, while it frequently shines in summer. Here are the average sunshine hours per day.
Portoroz - Sunshine
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Hours35668910107543

The sea temperature is high enough for swimming in July and August, but all in all, even in September.
Portoroz - Sea temperature
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Temp (°C)121111131822242523191614
Temp (°F)545252556472757773666157

In the cities that are not located right on the coast, the winter is a bit colder, as is the case of Nova Gorica and Ajdovscina, but the average is still above freezing, around 4/5 °C (39/41 °F) in January.

Inland areas



As soon as you move towards the interior, you will find some elevations, which are able to reduce the mild influence of the Adriatic Sea. Already in Postojna, located in the Karst Plateau, at 530 meters (1,700 feet) above sea level, winter is cold and snowy, while summer can be hot during the day, but nights remain cool. Rainfall is abundant throughout the year, with a relative decrease only in January, February, and July; in autumn, it can sometimes be torrential.

Ljubljana

In Ljubljana, at 300 meters (1,000 feet) above sea level, the monthly average temperature ranges from 0 °C (32 °F) in January to 21 °C (70 °F) in July. In winter, snow often falls, while in summer, there is a moderate amount of afternoon thunderstorms, although the sun shines quite often. In winter, there are frequent fogs when the weather is stable, while cold waves from Russia can bring intense frosts; in summer, there can be short heat waves, with peaks of 35 °C (95 °F). Here are the average temperatures.
Ljubljana - Average temperatures
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Min (°C)-3-21591315141172-2
Max (°C)36111521242726221583
Min (°F)272834414855595752453628
Max (°F)374352597075817972594637

Rainfall is abundant here as well, about 1,400 mm (55 in) per year, in fact, this is one of the rainiest capitals in Europe. Here is the average precipitation.
Ljubljana - Average precipitation
MonthJanFebMarAprMayJunJulAugSepOctNovDecYear
Prec.(mm)9090751001201351151301401501301151390
Prec.(in)3.53.533.94.75.34.55.15.55.95.14.554.7
Days99891313998111211121

The sun in Ljubljana is rarely seen in winter, while in summer, it shines quite often, though not as often as along the coast.
Ljubljana - Sunshine
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Hours245688996422

Ljubljana

Across the central and eastern part of Slovenia, the climate is similar to that of Ljubljana, and the differences are mainly due to the altitude. Going to the east, however, annual precipitation gradually decreases: in Maribor, it drops to 875 mm (34.5 in), mainly because autumn and winter are relatively less rainy, while summer equally receives its load of thunderstorms. This applies to the entire eastern area, from Maribor to the north-eastern flat area, on the border with Austria and Hungary.

Mountains



In high mountains, the climate is naturally colder. Snowfalls are especially abundant in the mountains of western Slovenia, on both the northern Alpine sector and in the massif to the south, which, not coincidentally, is called "snowy mountain" (Snežnik).

Kraniska Gora

In Kranjska Gora, a ski resort near the border with Austria, 800 meters (2,600 feet) above sea level, 1,740 mm (68.5 in) of rain or snow fall per year, and even more in the mountains that surround it. Here, strong afternoon thunderstorms can occur in summer, as well as heavy rains in autumn, especially in October. Here are the average temperatures.
Kraniska Gora - Average temperatures
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Min (°C)-8-7-3058101062-3-7
Max (°C)1481217202323181362
Min (°F)181927324146505043362719
Max (°F)343946546368737364554336

Best Time



The short coastline of Slovenia is good for a beach holiday in summer, especially in July and August, even though there can be some cool and rainy days, or some afternoon thunderstorms.
You can visit the interior from June to September, bearing in mind, however, that the rains may sometimes be heavy even in summer in the western areas, such as in Ljubljana or Postunia. In July and August, every so often, periods of intense heat may occur, so if you don't like the heat, you may prefer June and September.
In the mountain resorts, there is almost always enough snow. In February, the days are longer than in the Christmas period, so it can preferable for a ski holiday.

What to pack



In winter: in the interior, bring warm clothes, such as a sweater, a down jacket, a scarf, gloves, and an umbrella. On the coast, bring warm clothes, a jacket, a raincoat or umbrella, but also a hat, a scarf, and gloves for the days with Bora.
In summer: bring light clothes, T-shirts and shorts, but also long pants, a jacket and a sweatshirt for the evening or for cooler days; a raincoat or umbrella. In the mountains, bring hiking shoes, sunscreen and sunglasses.

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