For many, June 2021 will surely be remembered as a month with a “hellish” heat wave. But what do the numbers say? Let’s have a look!
We analyzed three meteorological quantities – precipitation, number of days with precipitation and temperature – for five Croatian cities: Zagreb, Osijek, Rijeka, Zadar and Dubrovnik. Here’s what the numbers say.
Precipitation
Compared to the multi-year average, from 2000 to 2020, this June was definitely below the 2000-2020 average, except for Osijek, which was somehow “normal”. The reason for such small amounts of precipitation is the small number of cyclone crossings over our region. This is how dry the beginning of the first decade of this millennium was.
Precipitation [mm]
| City / year | 2021 | 2020 | 2000-2020 | Min / year | Max / year |
| Zagreb | 13,5 | 103,1 | 86,4 | 29,3 / 2002 | 146,5 / 2014 |
| Osijek | 75,8 | 71,5 | 70,9 | 10,6 / 2003 | 188,5 / 2010 |
| Rijeka | 5,0 | 170,9 | 75,1 | 13,8 / 2003 | 170,9 / 2020 |
| Zadar | 30,2 | 101,9 | 38,2 | 0,1 / 2000 | 101,9 / 2020 |
| Dubrovnik | 5,0 | 45,1 | 55,1 | 0,2 / 2017 | 180,5 / 2014 |
The last two columns of the precipitation table show that the amplitudes of the monthly precipitation amounts in June are quite large. So they range from 0.2 to 180 mm in the case of Dubrovnik or from 10.6 to 188 mm in the case of Osijek. In other words, everything is natural in the sky.
Maximum daily precipitation for June 2021
| Station | Percip. max [mm] | Date |
| Dubrovnik Gorica | 3 | 10 June 2021 |
| Gospić | 14 | 7 June 2021 |
| Osijek Čepin | 7 | 8 June 2021 |
| Rijeka Kozala | 3 | 6 June 2021 |
| Zadar Puntamika | 2 | 7 June 2021 |
| Zagreb Maksimir | 7 | 6 June 2021 |
When we look at the number of days with precipitation, i.e. the number of days in which a certain amount of precipitation was recorded, we see that all the observed cities “failed”, especially Zagreb, Osijek and Rijeka.
Number of days with precipitation
| City | 2021 | 2020 | 2000-2020 | Min / year | Max / year |
| Zagreb | 4 | 18 | 11,4 | 5/2000 & 2002 | 18/2020 |
| Osijek | 3 | 17 | 11,1 | 2/2003 | 18/2009 |
| Rijeka | 2 | 14 | 9,2 | 3/2003 | 14/2008 & 2014 |
| Zadar | 2 | 13 | 6,4 | 1/2000 | 14/2009 |
| Dubrovnik | 2 | 5 | 5,2 | 1/2011 & 2017 | 13/2018 |
Temperature
Seen through the prism of temperatures, this June was significantly warmer than last year and the multi-year average. And again, this is caused by the rare movement of cyclonic systems over our region, many clear or slightly cloudy days and the influx of warm African air.
Average monthly temperature [°C]
| City | 2021 | 2020 | 2000-2020 | min | max |
| Zagreb | 25,4 | 21,9 | 22,6 | 20 / 2001 | 25,7 / 2003 |
| Osijek | 25,1 | 21,6 | 22,3 | 20,6 / 2009 | 26,2 / 2003 |
| Rijeka | 25,9 | 22,1 | 21,3 | 18,3 / 2001 | 27,1 / 2003 |
| Zadar | 25,2 | 22,9 | 23,2 | 21,2 / 2001 | 25,6 / 2019 |
| Dubrovnik | 25,5 | 22,5 | 24,1 | 22,5 / 2020 | 27,1 / 2003 |
On the graph above with average daily air temperatures, quite large jumps are easily observed, and the amplitudes are from 5 to 9 ° C, which is a significant amount.
The lowest daily temperature is measured in the period from 6 pm the previous day to 6 am the current day, and the highest from 6 am to 6 pm.
The table below shows that the highest measured June temperatures in all observed cities exceeded 30 ° C, and in Osijek and Zagreb 35 ° C.
Highest and lowest temperatures for June 2021
| Station | Tmin [°C] | Date | Tmax [°C] | Date |
| Dubrovnik Gorica | 17,5 | 1 June 2021 | 34,6 | 23 June 2021 |
| Gospić | 4,4 | 1 June 2021 | 34,1 | 23 June 2021 |
| Osijek Čepin | 7,4 | 1 June 2021 | 38,0 | 24 June 2021 |
| Rijeka Kozala | 12,7 | 2 June 2021 | 33,7 | 23 June 2021 |
| Zadar Puntamika | 15,5 | 1 June 2021 | 32,4 | 28 June 2021 |
| Zagreb Maksimir | 9,8 | 1 June 2021 | 35,6 | 24 June 2021 |
Looking at June on a planetary scale, the northern hemisphere was slightly warmer and the southern slightly cooler than the multi-year average. It was only +/- 0.3 ° C, but enough for unusual heat or cold. The extreme deviation was in Antarctica which was almost 7 °C cooler!
As our eyes are always on the future, you can check what awaits us in the coming days at www.meteo-info.hr!
Nebojša Subanović, mag. phys. geophys., meteorologist
Professional Associate at the Department of Environmental Engineering