The climate of Bosnia and Herzegovina

Due to geographical and climatological influences, the climate of Bosnia and Herzegovina is rather complex and determined by its geographic position. The Adriatic Sea strongly affects the climate, especially during colder months, when it emits huge amounts of thermal energy and tempers extreme winter temperatures. Altitude and relief, and particularly spatial distribution of mountain massifs, valleys and basins, karst fields, etc. affect the climate significantly. The Dinaric system has a particularly strong effect on the climate, since the mountains serve as a natural obstacle, blocking the cool air masses from the north, and warm air masses from the south. Karst basins and large river valleys allow passage of cool air masses from the north and warm air masses from the south that carry influences of the Central European continental climate and of the Mediterranean climate. Vegetation and snow cover affect the character of climatological elements, modifying the climate of the specific area. The climate is also affected by the cyclonic activity above the country, as well as by many local influences.

 Three types of climate dominate the territory of Bosnia and Herzegovina:

  1. Continental / Temperate Continental Climate,
  2. Mountain / Mountain-Basin Climate,
  3. Mediterranean / Modified Mediterranean Climate. (Source: INC 2009)

Continental climate is found in the north, Mediterranean in the south, and the line separating them is formed of high mountains, plateaus, and canyons where, depending on the altitude, the mountain climate dominates.

Continental and temperate continental climate

Continental and temperate continental climate is found in the northern Bosnia region, and in the valleys along the middle course of rivers Una, Sana, Vrbas, Bosna and Drina. The Sava River defines the northern border of this area, while the south is defined by a line connecting Bihać, Sanski Most and Banja Luka, through the valley of the Usora River and the Spreča River, all the way to Zvornik. Annual diagram of air temperature shows a sudden increase in temperature from January to July, followed by a gradual decrease towards December. The coldest month is January, the warmest is July. Mean January temperatures are negative, ranging from -0.9°C to 0.0°C, except in the area surrounding Bihać, where mean January temperature is above zero (0.3°C), due to specific position and orography.

The warmest month is July with mean values between 20°C and 22°C. Due to major differences between the warmest and the coldest month, annual temperature fluctuations are rather detectable (20°C - 23°C), even more than fluctuations in the mountains, which is typical of the continental climate.

Mean annual air temperatures are relatively high, ranging from 9.6°C to 11.4°C, with clearly distinct seasons. Spring and autumn feature some major temperature fluctuations, often resulting in late spring or early autumn frost that may have negative consequences.

The frost-free period varies considerably in this area, ranging between 174 and 206 days, meaning that the occurrence of frost is possible six months a year. Only the period from May to September is frost-free.

Mean minimum air temperatures are below zero in January, February, and December, lowest being January temperatures ranging between -5°C and -6°C.

Very high mean maximum temperatures in July and August (between 25°C and 27°C) lead to the conclusion that summers are relatively hot in this area.

Major differences in spatial distribution of temperature and its parameters depend on local influences. Based on the presented temperature regime, it may be concluded that this area is characterised by warm summers, cold winters, hence the prominent annual fluctuations, all being a result of the continental climate effects. Regarding precipitation, this area is typically dry with relatively low levels of precipitation, which makes it one of the driest areas in the country. Geographical distribution shows increase going from the north southwards, and from the east westwards. The highest levels of average annual precipitation are recorded in the northwest (1000 to 1500 mm), while the lowest precipitation levels are recorded on the outskirts of Bijeljina, Orašje and Bosanski Šamac (> 800 mm).

However, although the precipitation is rather scarce, it is very well distributed throughout the year not leaving the area dry. Maximum precipitation is typical of spring months (May-June), and the minimum is recorded in February and March. Besides the main maximum in spring, there is a second maximum in autumn (October - November). Spring precipitation maximum is a result of increased cyclonic activity above the country at this time of year, while the secondary maximum is affected by maritime factors. Favourable distribution of precipitation over the year is evident from low relative fluctuations (this area recording the minimum), as well as relatively large number of precipitation days ranging between 90 and 150 a year.

Annual distribution of precipitation shows that this area has a continental pluviometric regimen, albeit affected by maritime influence. Given the fact that this is an agricultural area, snow cover is of great importance since it protects the crops from severe frosts during the winter and creates large water supplies in the soil. The number of days with snow cover increases from the north southwards and from the east westwards, which is to be expected as the altitude, on which the duration of snow cover depends, increases in these directions. In the northern parts, the snow cover lasts between 40 and 60 days, and in the zone bordering with the mountainous area - up to 90 days. The average snow depth is 30 - 40 cm.

Annual distribution of cloudiness shows that winters are cloudier, while summers record low cloud cover (under 50%), which explains long sunshine duration in this area.

Geographical distribution is characterised by a wide strip of increased cloudiness stretching from Bosanska Dubica and Bosanska Gradiška towards the south, and by a narrow area surrounding Bihać.

Average sunshine duration is rather high ranging from 1730 to 1920 hours. Over the year, the sunny days peak in July, with an average of 8.4 hours of sunshine a day, and hit the lowest point in December, when the average daily sunshine duration is 1.7 hours.

Mountain climate and mountain-basin climate

Mountain-basin climate starts from the border of the northern area. In the south, the border is a line linking Posušje, southern slopes of Čabulja, Velež, Bjelašnica, and Bileća.

This area is under influence of the North-European continental climate coming from the north and the Mediterranean climate coming from the south. Since these climates are interwoven, and the relief is rather diverse, this area is left with the features of a tempered mountainous climate. Spatial distribution of air temperature shows major differences between relatively close locations of as high as 11°C.

The coldest month is January, with mean values between -0.3°C and -6.5°C, and the warmest is July or August, with values from 9.5°C to 21.2°C. Autumn is warmer than spring due to thermal influence of the Adriatic Sea.

Mean annual air temperature ranges between 1.2°C to 11.6°C. Since the thermal influence of the land surface is buffered here, annual temperature fluctuations are not as prominent as in northern areas. The average value is about 20°C. The smallest difference is found in the spatial distribution of January temperatures, and the greatest in those of July and August. This can be explained by different effects of modifiers over the year. The Adriatic Sea, having accumulated large reserves of heat during summer months, emits the heat during winter months and tempers low winter temperatures; in summer, when the sea is cooler than the land, it tempers extremely high summer temperatures. In winter months, rather complex relief causes some minor changes in the temperature due to the differences in altitude. In fact, air deposits in basins form “lakes” of cool air causing inversion – an increase in temperature with altitude - so lower altitudes often record lower temperatures.

Highest mean maximum temperatures, in almost the entire area, occur in August, with the exception of some areas where they occur in July, ranging from 12.3°C to 29°C. The delay of extreme temperatures typical of August is a result of the maritime influence. Typical of this area is that mean monthly temperatures are negative in almost three months (December, January, February).

Mean minimum temperature values are relatively low and range from -1.9°C to -8.8°C in January. In these areas, negative temperatures occur early (at the beginning of autumn), but also late frosts (in spring) are common. Duration of the no-frost period varies significantly, so on Bjelašnica it lasts only 86 days, while in Višegrad - 219 days.

Spatial distribution of the annual precipitation is uneven due to the complex relief. Windy sides of high mountains have high annual levels of precipitation ranging between 1500 and 2300 mm, while in sheltered river valleys and basins the precipitation is at 700-800 mm. In addition to much greater precipitation quantity, high mountains have more days with precipitation than the surrounding valleys and basins. Regarding the number of days with precipitation above 1.0 mm in this area, Bjelašnica leads with 163, while Čajniče is the last with 93 days. In addition, the greatest intensity of daily and hourly precipitation is recorded in this region.

Annual distribution per month also shows major variations. Precipitation peaks in October, November, and December, and drops to the lowest values in summer months of July and August, and in some parts of East Bosnia, in February and March.

Snow has a significant share in the annual precipitation, since it is a regular phenomenon in the cold six months; the share of snowfall in annual precipitation volumes is 40-50%. Number of snow days and snow depth increase with altitude. The first snow cover will occur in November, and the last in April. High mountains are an exception, since the snow forms a cover much earlier, and it melts much later.

Height and duration of snow cover do not only affect the climate, but also serve a practical purpose in different industries. The snow cover is not only useful in agriculture; it is also important in water and energy management, since melting snow increases water level of rivers.

Annual distribution of cloudiness shows that winter is the cloudier part of the year. However, spatial distribution shows major differences. Due to common fogs in basins and valleys, mountainous areas feature less cloudiness than the lowlands. Mean annual cloudiness ranges between 52% and 69%. The cloudiest is the zone in the central part of the country, stretching south-east and covering a major part of East Bosnia. Since sunshine duration is closely related to cloudiness, it lasts longer in areas of low cloud cover.

Annual distribution of sunshine duration per month also shows major variations. Insolation is longest in July and August, and shortest in December. During winter, mountains receive more sunshine than valleys and basins, therefore, they record significantly higher insolation values. A good example is to compare Bjelašnica data and Sarajevo data. In December, Bjelašnica has 82.9 hours of insolation, while Sarajevo merely 40.8 hours. However, the annual sum of sunshine duration shows that Sarajevo has 70 hours more, indicating that Sarajevo is much less cloudy during summer compared to Bjelašnica.

Indicated characteristics of climatological elements and their parameters, in both the annual and the spatial distribution, clearly show that this area is affected by numerous mezzo-climatic types, making this a transition zone between the continental and the mountain climate.

mediterranean (adriatic, subtropical) climate

Mediterranean (Adriatic, Subtropical) climate is found in the southwest of the country, in Herzegovina. This area is situated between the southern border made of hills and mountains, and the official state border on the south. Proximity of the Adriatic Sea and its direct influence on climatological elements give this area some of the maritime features. Prominent relief, especially distribution and direction of the relatively high mountain masses, reduce the maritime influence to a narrow area causing a sudden switch from the maritime to the continental conditions. Only river valleys of Neretva and Trebišnjica allow these influences to reach deeper inland.

Mean annual air temperatures are relatively high at 12.8°C in Široki Brijeg, and 15.2°C in Neum. Annual fluctuations of this climatological element show that January is the coldest, and July the warmest month. Mean January air temperature is positive in this area, and ranges between 3.4°C in Široki Brijeg and 6.6°C in Neum.

Mean July temperatures range between 22.6°C and 24.7°C. Autumn is always warmer than spring as a result of the strong maritime influence. Spring increases and autumn decreases in air temperature are much slower compared to the areas deeper in the continent, where they tend to be more sudden. This area shows mild annual fluctuations ranging between 19.3°C and 21.4°C. Lower temperature values and greater fluctuations are caused by altitude, but also by local influences.

Distribution of mean maximum air temperatures shows the highest values in August ranging between 29°C and 31°C. Such high values of mean maximum temperatures result from the weakened influence of the Adriatic Sea during summer months.

Mean minimum air temperature values range between -1.7°C and 3.4°C. Negative values occur only in areas of higher altitude and more complex relief. It should be noted that frost is typical of this area, but mostly during winter months, occasionally occurring in late autumn and early spring. Frost begins in the second half of November or in early December, and ends in March.

Precipitation is scattered in this area and depends on the season and the location. Spatial distribution of annual precipitation volumes shows extreme differences. The lowest precipitation volume is recorded in Čapljina (1070 mm), and the highest in Vrbanj (Orijen) - 3347 mm. Such major differences in annual precipitation volumes is are caused by the relief and its effect on humid air masses coming from the south and ascending over windy slopes where they release abundant precipitation. Annual distribution of precipitation over the months shows prominent winter maximum and summer minimum of precipitation. Months with highest levels of precipitation are November and December, with values between 141 mm in Čapljina and 496 mm recorded at the precipitation station Vrbanj. (Orijen). July and August are the driest with 34 mm in Čapljina and 66 mm in Vrbanj (Orijen).

With such great differences in precipitation volumes throughout the year, it is clear that fluctuations will have the highest values in this area as well. Mostar is characterised by low fluctuations, and Vrbanj (Orijen) by the highest, which indicates that precipitation is more evenly distributed in Mostar than in Vrbanj (Orijen).

Extreme differences between the maximum and minimum precipitation volumes, as well as major relative fluctuations, are typical of the maritime pluviometric regime. The number of precipitation days is also much greater during winter months compared to summer months. Snow typically occurs very rarely; these are usually isolated events during winter, and their share in the annual precipitation volume is negligible. Since the number of snow days is rather small, forming of snow cover is rather rare in this area. The first snow cover is formed in the second half of January, and the last in early February. Exceptions include higher altitude locations, where snow cover occur somewhat earlier/later.

Regarding cloudiness, this area is one of the clearest in our country, with mean annual values ranging between 46% and 53%. Annual overview shows that cloudiness peaks in December and November, and reaches its lowest values in August. It is interesting to mention that, even in the cloudiest part of this area, mean July cloudiness does not exceed 28%.

Such low values of cloudiness explain long sunshine duration in this area with more than 2286 hours per year, and more than 10.4 hours on an average July day. With such high values of sunshine duration, this area is one of the sunniest, not only in our country, but in Europe.

It was not possible to include all local deviations due location, relief, altitude, etc. in the presented spatial and annual distribution of climatological elements.

Köppen Climate Classification

Out of many climate classifications based on different principles, we will present one of the most applicable - the Köppen Climate Classification. It is based on distinguishing climates based on their thermal and pluviometric regime, i.e. average monthly values of temperature and precipitation in a multi-annual period.

The Köppen classifies the basic climate types using letters: A, B, C, D, and E.

According to the Köppen classification, the reference period 1961-1990 on the territory of Bosnia and Herzegovina shows three climate classes: type C and type D as moderately warm and moderately cold, and type E climate - cold climates.

Climate type

Climate subtype

 

Description

C

Cf

Cfa

Moderately warm and rainy climate with hot summers

- Mean monthly temperature in the hottest month is ≥ 22°C. No extremely dry periods.

Cfb

Moderately warm and humid climate with warm summers

- Mean monthly temperature in the warmest month is < 22°C, at least 4 months with mean monthly temperature ≥10°C.

Cs

Csa

Mediterranean climate with dry and hot summers

- Mean monthly temperature of the warmest month is > 22°C with rather prominent daily amplitudes of air temperature in the summer part of the year.

Csb

Mediterranean climate with dry and warm summers

- This climate is a modification of the Csa climate, since it is a somewhat cooler and more humid. Mean monthly temperature in the warmest month is < 22°C, while the mean monthly temperature of the coldest month ranges between 4 and 13°C.

D

Df

Dfb

Moderately humid climate with warm summers

- Mean monthly temperature in the warmest month is ≤ 22°C; at least 4 months with mean temperature of ≥ 10°C.

Dfc

Moderately humid climate with cool summers

- Long and very cold winters with short and cool summers.

E

ET

 

Tundra climate

- Mean monthly temperature in the hottest month: 0.0°C< t ≤10.0°C

Climate types according to the koppen climate classification
Climate diagrams for climate types ET, Cfb and Csb