Croatia, Slovenia: Adverse weather forecast across both countries through at least June 23

Event

Severe weather is forecast across much of Croatia and Slovenia through at least June 23. Thunderstorms are expected to break out amid high temperatures across the region. Storms may be accompanied by heavy downpours, lightning, and possible hailstorms. Heavy downpours could trigger flooding in low-lying areas and strong winds could cause property damage and power outages. Temperatures could reach as high as 36 C (97 F) in parts of the region over the coming days, which will pose a health risk and cause possible disruptions.

The meteorological agencies for the respective countries have issued the following weather warnings June 21:

• Orange thunderstorm warnings: Northeastern regions in Slovenia.

• Orange high temperature warnings: Zagreb Region in Croatia and central and southeastern regions in Slovenia.

• Yellow thunderstorm warning: Zagreb Region in Croatia and northwestern and southeastern regions in Slovenia.

• Yellow high temperature warnings: Karlovac Region in Croatia and northeastern and northwestern regions in Slovenia.

Further orange and yellow high temperature warnings are in place across Croatia and Slovenia June 22 and yellow thunderstorm and high temperature warnings have been issued across Slovenia June 23. Officials could update and possibly extend the coverage of the weather alerts over the coming hours and days.

Hazardous Conditions
Sustained heavy rainfall could trigger flooding in low-lying communities near rivers, streams, and creeks. Urban flooding is also possible in developed areas with easily overwhelmed or a lack of stormwater drainage systems. Sites located downstream from large reservoirs or rivers may be subject to flash flooding after relatively short periods of intense rainfall. Landslides cannot be discounted in hilly or mountainous areas, especially where the soil has become saturated by heavy rainfall. The adverse weather conditions could cause power outages throughout the affected area.

Persistent high temperatures may produce ideal circumstances for wildfire growth throughout the region. Heatwaves also pose a threat to vulnerable groups - such as the elderly, children, pregnant women, and those with respiratory illnesses - due to the increased possibility of heat stroke or heat exhaustion during prolonged exposure to high temperatures. These health risks could also extend to relatively healthy individuals during significant heatwave events.

Transport
The severe weather could contribute to transport disruptions throughout the region. Traffic and commercial trucking delays might occur along regional highways. Strong winds might pose a hazard to high-profile vehicles. Floodwaters and debris flows may render some bridges, rail networks, or roadways impassable, impacting overland travel in and around affected areas. Authorities could temporarily close some low-lying routes that become inundated by floodwaters.

Very high temperatures may warp rail tracks and force passenger and freight trains to operate at reduced speeds. Road surface damage is also possible, and overheated vehicles may worsen traffic problems in urban areas where congestion is already a problem. Commercial trucking disruptions might occur as very high temperatures stress vehicles, making tire blowouts more common. Major flight disruptions are unlikely, but general aviation disruptions are possible, and some airfreight carriers could reduce cargo loads. High temperatures could lead to an increased demand for electricity, which might trigger localized brownouts or blackouts, exacerbating hazardous conditions when air conditioning is no longer possible.

Advice

Monitor local media for weather updates and related advisories. Confirm all transport reservations and business appointments prior to travel. Make allowances for localized travel delays, as well as potential supply chain disruptions, where severe weather has been forecast. Do not drive on flooded roads. Charge battery-powered devices in the case of prolonged electricity outages.

During heat waves, remain indoors in air conditioning when possible. If outdoor activities are necessary, frequently rest in shaded areas; avoid activity during the hottest times of the day. Stay well hydrated by drinking plenty of fluids. Avoid alcoholic beverages, which are dehydrating - drink bottled water or water that has been boiled. Wear loose-fitting, light-colored clothing. Cotton fabrics are more cooling than synthetics. Promptly seek medical attention if signs of heat exhaustion or heat stroke develop.

Resources

MeteoAlarm
Croatian Meteorological and Hydrometeorological Service (DHMZ)
Slovenian Environment Agency (ARSO)