The climate of Croatia

The greatest part of Croatia has a moderately warm, rainy climate. The mean annual air temperature in the lowland area of northern Croatia is 10-12°C. Above 400 m it is lower than 10°C, while in the highland it is 3-4°C. In the coastal area annual air temperature is 12-17°C.

January is the coldest month on average, with the temperature in the Pannonian region ranging from 0 to -2°C. Along the Adriatic coast winters are milder; January temperatures are 4-6°C. In the north and east of Croatia average July temperatures are 20-22°C and on the Adriatic coast 23-26°C (1).

The least precipitation in Croatia is recorded in the open part of the central Adriatic (304 mm) and in the eastern Slavonia and Baranja (650 mm). Central Croatia and the coastal zone have 800-1,200 mm precipitation per year. The precipitation amount in the Pannonian area decreases from the west to the east. The precipitation amount increases from the coast to the inland. Most of the precipitation is recorded on the slopes and peaks of the coastal Dinarides.

Air temperature changes until now

Increase of mean annual air temperature, which in the 20th century was between +0.02°C per 10 years (Gospić) up to +0.07°C per 10 years (Zagreb), continued and amplified by the beginning of the 21st century. It has become particularly expressed within the last 50 years, even more within the last 25 years. The positive temperature trends in the continental part of Croatia is mostly due to winter trends, and on the Adriatic due to summer trends (2).

Both globally and in Croatia, the period between 1991 and 2000 was the warmest decade of the 20th century. The greatest contribution to warming in the coastal part is from temperatures of the warm season: autumn on the island of Hvar and summer in Crikvenica, while in the mainland areas the winter temperatures increased most (1).

In the period 1951–2010, a statistically significant increase in the mean annual temperature of 0.07–0.22°C per decade is present along the Croatian coastal zone. This increase is further amplified within recent shorter periods. For example, in the period (1981–2010), it ranges from 0.28 to 0.71°C per decade. Five to seven out of ten warmest years since the middle of the twentieth century were recorded in the most recent decade 2001–2010. Temperature trends are positive in all seasons. In the first decade of the twenty-first century, they are statistically significant at the 0.05 level for summer (0.19°C/10 years to 0.38°C/10 years) and spring (0.12°C/10 years to 0.29°C/10 years), but positive trends for winter and autumn are comparably weak (3).

The summer of 2012 was very hot and dry in South-East Europe; it was the hottest and third-driest on record in Serbia (4). For this part of South-East Europe (including parts of Northern Serbia and Southern Hungary, as well as smaller areas in Bosnia-Herzegovina, Croatia and Romania), the change of the likelihood of an extreme summer such as the one of 2012 between the decades of 1960-1970 and 2000-2010 was assessed. This was done by studying decade-long model simulations (general circulation model and an embedded dynamical regional climate model) and observations. From this study it was concluded that the magnitude and frequency of heat waves have increased considerably in South-Europe between the 1960s and the 2000s. In addition, indices combining temperature and precipitation to assess changes in dryness and heat stress risk have been analysed; these results also show an increase in return time, although the results are subject to uncertainties (5).

Precipitation changes until now

Croatia is a climatically complex area with a large variability in precipitation trends over the last decades from one location to another. Annual precipitation trends in Croatia during 1961–2010 are mostly weak and downward (negative), reflecting the characteristics of the Mediterranean regime (1,2,7). Particularly, the mountainous region and the coastal hinterland are mostly affected by drying tendencies in precipitation, especially during summer season, while the mainland is subjected to wetter precipitation conditions (7). Others found that downward precipitation trends are more marked in the northern Adriatic (Crikvenica -18%), on Dalmatian islands (Hvar -12%) and in eastern Slavonia (Osijek -13%) than in the mountains (Gospić -8%) and in northwestern Croatia (Zagreb -3%) (1,2). The fall in annual amounts of precipitation in the area north of the Sava River results from decline in spring and autumn precipitation. In the mountains and on the Dalmatian islands the fall results from decline in winter and spring precipitation. On the northern Adriatic the fall in precipitation amountis evident in all seasons (1,2).

Along the Croatian coastal zone interannual variability of annual precipitation during the period 1951–2010 is large and there are practically no significant trends in either annual or seasonal precipitation amounts for the different parts of the country (3). This was confirmed by an analyses of data over the period 1961−2010 (6).

The analysis of trends in precipitation extreme indices showed a positive trend in the annual number of dry days significant at the level of 5% in the area of Adriatic and Zagreb. At the same time the negative trend of wet days is negligible and the number of wet days remained unaltered (1).

Results of trend analysis indicate prevailing increase of mean annual duration of dry spells (2):

• when defined as a sequence of days with daily precipitation amount (Rd) less than 1 mm, it is statistically significant in Istria (5 to 6%/10 years) and on southern islands (Hvar and Lastovo 5%/10 years). Increase of dry spells on annual basis is a result of prevailing increase in all seasons, except in autumn.
• when defined as s a sequence of days with daily precipitation amount (Rd) less than 10 mm, results indicate a prevailing positive trend in Croatia, significant in Istria and Dubrovnik (6 to 8%/10 years). Statistical significance of trend at annual scale is mostly forced by winter and summer significant increase of mean dry spells. Maximum dry spells have increased along the coast (10 to 11 %/10 years) and reduced in the inland (8 %/10 years). Prevailing increase of dry spells at the Adriatic, as well as poorly expressed trend in the continental area contribute to the fact that Croatia remains within the transitional area between the northern Europe with general tendency of precipitation increase, and the drying Mediterranean (2).

Large amounts of precipitation that fall on very wet days almost do not change. Absolute annual, one-day and five-day maximums show a high variability among years, with a negative sign for five-day maximums across Croatia and one-day maximums in lowland and highland areas. The reduction in the annual amounts of precipitation can be attributed to changes in the incidence of low-intensity rain days and the increased incidence of dry days (1,2).

However, an analysis of the annual maximum precipitation amount that fell in the region of Zagreb during periods of 30 to 120 minutes showed an increase of up to 2.9%/10 years in the period 1908–2020 (11).

Heat wave and cold wave changes until now

In the Carpathian Region (encompassing Croatia, Hungary, Slovakia, Czech Republic, Poland, Ukraine, Romania and Serbia), heat wave events have become more frequent, longer, more severe and intense over the period 1961 - 2010, in particular in summer in the Hungarian Plain and in Southern Romania (8). Cold wave frequency, average duration, severity, and intensity over this period, on the other hand, generally decreased in every season except autumn. In this study, a heat wave was defined as at least five consecutive days with daily maximum temperature above the long-term 90th percentile of daily maximum temperatures. Similarly, a cold wave was defined as at least five consecutive days with daily minimum temperatures below the long-term 10th percentile of daily minimum temperatures (8).

The trend analysis shows a general tendency to more frequent, longer, more severe and more intense heat wave events in every season in the entire Carpathian Region. On the other hand, the cold waves show a general tendency to less frequent, shorter, less severe, and less intense events (8).

The Carpathian Region and the Mediterranean area are the two European hotspots showing a drought frequency, duration, and severity increase in the past decades and in particular from 1990 onwards (9). When drought effects are exacerbated by heat waves or vice versa, such combination may cause devastating effects, as it happened in summer 2003 in Central Europe (10). 

Air temperature changes in the 21st century

Projections of temperature increase for Croatia have been calculated for 2041-2070 compared with 1961-1990 (A2 scenario) (2):

• Winter: 1.8°C in the northern part and about 1.5°C in the southern parts of the country;
• Spring: relatively uniform warming throughout Croatia of about 1.5°C;
• Summer: 2°C in the northern and almost 3°C in the southern part of the country;
• Autumn: warming between 1.5°C in a larger portion of the continental Croatia and slightly above 2°C in the coastal zone, as well as in Istria and the Dalmatian hinterland.

In many areas, the number of hot days, with maximum temperatures higher or equal to 30°C, will be doubled by the middle of this century. For example, the increase will be from 6 days in mountainous areas up to almost severe 20 days at the Adriatic (2).

Climate change projections have been made for the future 30-year periods 2011–2040, 2041–2070 and 2071–2100, and compared with the period 1961–1990. This has been done for five different RCMs, driven by one GCM, and based on the IPCC SRES A1B scenario. The mean annual trend of projected future warming for the period 2011–2100 is between 0.3 and 0.5°C per decade. The results show a statistically significant warming in the eastern Adriatic region in all three 30-year periods of the twenty-first century. The largest temperature increase is projected for the summer and early autumn, gradually rising from +2°C in the near future to +5.5°C towards the end of the twenty-first century, respectively (3).

Precipitation changes in the 21st century

Projections of precipitation changes for Croatia have been calculated for 2041-2070 compared with 1961-1990 (A2 scenario) (2). These projections show total precipitation decrease in three seasons (spring, summer and autumn), primarily in coastal, southern and mountainous Croatia. The decrease is generally less than 0.5 mm/day (or 45 mm in a season). Only in winter there will be a slight precipitation increase, mainly in the littoral and mountainous part of Croatia, as well as in the northern and eastern parts (2).

In summer, a relative decrease of total precipitation along the eastern Adriatic coast and its inland (over 20%) is larger than in spring and autumn (less than 15%), as total precipitation is smallest in summer. In summer, this decrease is statistically significant, while in spring and autumn precipitation decrease in future climate is significant only in the southern part of the eastern Adriatic coast (t-test, 95% confidence level). Precipitation increase in winter is not significant (2). It could be concluded, therefore, that in future climate in most of the year there will be a deficit in precipitation in western and southern Croatia, while the increase in winter is not reliable. In northern parts of the country there will be no significant change in total precipitation in future climate (2).

The reduction of the height of snow cover is projected to be 1 mm in northern Croatia, up to slightly more than 2 mm in mountainous areas. Except in the north-western Croatia and Istria, the reduction of snow cover by the middle of this century is statistically significant (t-test, 95% confidence level). ... The number of days with snow is projected to be significantly lower in the future (50% at the end of the century) than today (2).

Climate change projections have been made for the future 30-year periods 2011–2040, 2041–2070 and 2071–2100, and compared with the period 1961–1990. This has been done for five different RCMs, driven by one GCM, and based on the IPCC SRES A1B scenario. In the first half of this century, projected precipitation change is uncertain. In the second half of this century a reduction of precipitation in the warmer part of the year (April – August/September) prevails and an increase of precipitation from December to February (March) prevails. These projected changes are statistically significant at only a few of the studied locations in the country, however (3).

For the Croatian Adriatic coast in the near-future (2011−2040) climate, changes in mean precipitation and indices of extreme precipitation (for the A2 emission scenario, compared with the period 1961−2010) are generally weak and mostly not statistically significant (6).

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 Croatia.

1. Republic of Croatia, Ministry of Environmental Protection, Physical Planning and Construction (2006)
2. Republic of Croatia, Ministry of Environmental Protection, Physical Planning and Construction (2010)
3. Branković et al. (2013)
4. Hydrometeorological Service of Serbia (2012b), in: Sippel and Otto (2014)
5. Sippel and Otto (2014)
6. Patarčić et al. (2014)
7. Gajić-Čapka et al. (2015)
8. Spinoni et al. (2015)
9. Spinoni et al. (2013), in: Spinoni et al. (2015)
10. Fink et al. (2004); Ciais et al. (2005), both in: Spinoni et al. (2015)
11. Nimac et al. (2022)