Slovenia is a transitional climate area between the Mediterranean Sea, the Alps, the Dinaric Mountains and the Pannonian Basin. As a consequence, its climate displays wide local climatic variability and fairly large gradients (3).

Air temperature changes until now

Slovenia’s climate is extremely diverse. Near the coast, the prevailing type of climate is sub-Mediterranean, in mountains Alpine, while the continental climate prevails in the flat parts of eastern Slovenia (1).

From the middle of the 1980s on, above-average warm years have been very common, and the majority of the warmest years starting from the middle of the last century occurred in the last few years. In the last few years the summer heat waves have been appearing earlier, usually as soon as the end of spring. The summer of 2003 was extremely hot (1).

During the period 1951–2007, mean annual temperatures in Slovenia have increased significantly by 0.15 to 0.29°C/decade (4). A stronger increase of annual mean, maximum and minimum temperature during 1961-2011 of 0.3 to 0.4°C/decade was reported by (6). Seasons show different trends (4):

• Spring and summer: A significant increase of 0.3-0.4°C per decade was observed in extended areas of central and north-eastern Slovenia during spring and summer.
• Autumn: No significant trends were observed in autumn over most of the Slovenian area.
• Winter: A significant increase of 0.2–0.3°C/decade was observed in central and north-eastern parts of Slovenia.

The strong warming in summer and spring, that is almost twice the trend observed in neighbouring countries, could be enhanced by drier soils caused by the decrease in winter precipitation in Slovenia (4).

Precipitation changes until now

The maximum annual precipitation is in the northwest in the Julian Alps, where annual precipitation can exceed 3000 mm. On the coast, the annual precipitation usually does not reach 1000 mm, increases towards the top of the Alpine-Dinaric mountain ranges, and then decreases with the increasing distance from the sea towards the northeast. In the extreme northeast the precipitation is usually below 800 mm per year (1). The spatial distribution of annual precipitation is mainly caused by humid air masses from the Mediterranean, which moves with south-westerly flow towards the mountain barrier. The flow is perpendicular to the orographic barrier and is therefore forced to lift, which causes heavy precipitation events (4). Annual precipitation increases with altitude, at an average rate of 56 mm every 100 m. Such influence of altitude is higher in autumn, lower in winter and intermediate in spring and summer (4).

In European terms, Slovenia is among the areas with the highest number of storms. Each year these include several severe thunderstorms, during which more than 100 mm of precipitation may fall within one hour. Extreme daily precipitation may exceed 400 mm in the Posočje region. In 2005, torrential flooding caused major local damage on several occasions due to the intensity of precipitation (1).

During the period 1951–2007, changes in mean annual precipitation were observed only in the north-western part, where precipitation decreased at a rate of 3–6% per decade (4). Observed trends for the seasons are:

• Spring and summer: Significant trends were observed in the western part of Slovenia only: a decrease of 3–6 % per decade.
• In autumn: Trends were non-significant throughout Slovenia.
• Winter: Precipitation significantly decreased by 3–12% per decade; this trend was especially intense in the north-western part of Slovenia.

Snow cover changes until now

Over the last 50 years (1968–2017), the European Alps have experienced a decline in the winter snow depth and snow cover duration ranging from −7% to −15% per decade and from −5 to −7 days per decade, respectively, both showing a larger decrease at low and intermediate elevations (9). 

Air temperature changes in the 21st century

By the end of the 21st century, relative to the reference period 1981–2010, annual mean temperature in the Alps is projected to be 1 °C, 2 °C, and 4 °C higher under a low-end (RCP 2.6), moderate (RCP 4.5) and high-end (RCP 8.5) scenario of climate change, respectively. Strongest warming is projected for the summer season, for regions south of the main Alpine ridge. Depending on the season, medium to high elevations might experience an amplified warming (8). 

Based on the results of general circulation models, Slovenian territory can expect an increase in air temperature of 1 to 4°C in the first half of the 21st century compared to the average figures for 1961 to 1990 (1).

By the end of the 21st century, compared with the period 1961-1990, summer is projected to warm up the most (between 3.5°C and 8°C), followed by winter (between 3.5°C and 7°C), spring (between 2.5°C and 6°C) and autumn (between 2.5°C and 5°C) (2).

Precipitation changes in the 21st century

Based on the results of general circulation models, Slovenian territory can expect a change in precipitation of –20% to +20% in the first half of the 21st century compared to the average figures for 1961 to 1990. The most probable climate development in Slovenia in future is towards warmer and drier summers, warm winters with a similar quantity of precipitation and a higher frequency of extreme weather events (1).

By the end of the 21st century, compared with the period 1961-1990, an increase in precipitation is expected in the winter months (up to 30 %), and a decrease in precipitation in the summer months (up to 20 %) (2). In the Alps the more relevant extreme events such as those with 10-year return period remain in summer and increase strongly in intensity (7).

The frequency of heavy rainfall, hailstorms, floods, lengthy droughts (increased fire risk), and extremes of air temperature will increase (1).

Snow cover changes in the 21st century

Changes in mean winter snow water equivalent (SWE), the seasonal evolution of snow cover, and the duration of the continuous snow cover season in the European Alps have been assessed from an ensemble of regional climate model (RCM) experiments under the IPCC SRES A1B emission scenario. The assessment was carried out for the periods 2020–2049 and 2070–2099, compared with the control period 1971–2000. The strongest relative reduction in winter mean SWE was found below 1,500 m, amounting to 40–80 % by mid century relative to 1971–2000 and depending upon the model considered. At higher elevations the decrease of mean winter SWE is less pronounced but still a robust feature. For instance, at elevations of 2,000–2,500 m, SWE reductions amount to 10–60 % by mid century and to 30–80 % by the end of the century (5).

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Slovenia.

1. Republic of Slovenia, Ministry of the Environment and Spatial Planning (2006)
2. Bergant (2007), in: Republic of Slovenia, Ministry of the Environment and Spatial Planning (2010)
3. Ogrin (2004), in: De Luis et al. (2012)
4. De Luis et al. (2014)
5. Steger et al. (2013)
6. Vertačnik et al. (2015)
7. Brönnimann et al. (2018)
8. Kotlarski et al. (2023)
9. Monteiro and Morin (2023)