In Slovenia there is a clear separation between the western flat area stretching from Nova Gorica to northern Istria, which has a mild climate, and the interior, which has a moderately continental climate (in hills and valleys, and in the eastern plain) or a cold mountain climate (in the mountains).
Precipitation is abundant in the western part of the country, where it varies between 1,000 and 1,500 millimetres (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) in the most exposed slopes. Only in the far east, precipitation becomes less abundant, and decreases below 900 mm (35.5 in).



The western plains of Slovenia that are influenced by the sea are not vast, because about 30 kilometres (18 miles) away from the coast there is a mountain range that separates the interior from the sea. 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: the average temperature in January is around 5/6 °C (41/43 °F). This area is exposed to a fearful wind: the temperature undergoes sudden drops when the Bora makes its appearance, a cold and furious wind which may be accompanied by clear skies (light Bora), or more rarely by cloudy skies, with rain or snow (dark Bora). Snowfall in this area is rare and usually not abundant, because the Bora comes from the dry plains of Eastern Europe, therefore it's usually dry.
Here are the average temperatures of Portorož, located on the coast of the northern Adriatic Sea, on the Gulf of Trieste.
Average temperatures - Portoroz

Portoroz	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Portoroz	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	3	3	6	9	13	16	19	19	16	12	7	4
Max (°C)	6	8	11	15	19	23	26	26	22	18	12	8
Min (°F)	37	37	43	48	55	61	66	66	61	54	45	39
Max (°F)	43	46	52	59	66	73	79	79	72	64	54	46

Rainfall in Portorož is fairly abundant, around 1,000 millimetres (40 inches) per year, and is well distributed throughout the year, given that even in summer there can be some rain, often in the form of thunderstorms. However, the rainiest season is autumn. Here is the average rainfall.
Average precipitation - Portoroz

Portoroz	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Portoroz	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	65	60	70	80	85	100	75	90	110	125	105	80	1045
Prec.(in)	2,6	2,4	2,8	3,1	3,3	3,9	3	3,5	4,3	4,9	4,1	3,1	41,1
Days	9	8	8	14	11	10	9	9	11	12	14	11	126

In Portoroz and along the Adriatic Coast the sun does not shine very often in winter, while in summer the sunshine amount is good.
Sunshine - Portoroz

Portoroz	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Portoroz	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	3	5	6	6	8	9	10	10	7	5	4	3

The sea temperature is high enough for swimming in July and August, but all in all even in September.
Sea temperature - Portoroz

Portoroz	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Portoroz	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	12	11	11	13	18	22	24	25	23	19	16	14
Sea (°F)	54	52	52	55	64	72	75	77	73	66	61	57

In cities which 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.
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 in which Atlantic disturbances manage to move over the country, maybe accompanied with some cool gusts of Bora.

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



In Ljubljana, at 300 metres (1,000 feet) above sea level, the average of January is 0 °C (32 °F), that of July is 21 °C (70 °F). 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.
Average precipitation - Ljubljana

Ljubljana	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Ljubljana	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	90	90	75	100	120	135	115	130	140	150	130	115	1390
Prec.(in)	3,5	3,5	3	3,9	4,7	5,3	4,5	5,1	5,5	5,9	5,1	4,5	54,7
Days	9	9	8	9	13	13	9	9	8	11	12	11	121

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.
Average temperatures - Ljubljana

Ljubljana	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Ljubljana	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	-3	-2	1	5	9	13	15	14	11	7	2	-2
Max (°C)	3	6	11	15	21	24	27	26	22	15	8	3
Min (°F)	27	28	34	41	48	55	59	57	52	45	36	28
Max (°F)	37	43	52	59	70	75	81	79	72	59	46	37

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

Ljubljana	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Ljubljana	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	2	4	5	6	8	8	9	9	6	4	2	2

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 goes down to 875 mm (34.5 in), and especially autumn and winter are relatively less rainy, while summer receives equally 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.

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). In Kranjska Gora, at 800 metres (2,600 feet) above sea level, 1,740 mm (68.5 in) of rain or snow per year fall, and even more in the mountains that surround it. In summer, strong afternoon thunderstorms are possible, as well as heavy rains in autumn, especially in October. Here are the average temperatures.
Average temperatures - Kraniska Gora

Kraniska Gora	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Kraniska Gora	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	-8	-7	-3	0	5	8	10	10	6	2	-3	-7
Max (°C)	1	4	8	12	17	20	23	23	18	13	6	2
Min (°F)	18	19	27	32	41	46	50	50	43	36	27	19
Max (°F)	34	39	46	54	63	68	73	73	64	55	43	36

The short coastline of Slovenia lends itself to beach life in summer, especially in July and August, even though there can be some cool and rainy days, or some afternoon thunderstorms.
The interior can be visited from June to September, bearing in mind, however, that sometimes the rains may 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 ski resorts, snow is almost always guaranteed. In February, the days are longer than in the Christmas period, so it's preferable for skiing.


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