A major power outage has struck much of the Balkans as the southern European region sweltered in an early heat wave that sent temperatures soaring to up to 40C.

Montenegrin authorities said that an outage in the country’s power distribution system left almost the entire country without electricity, while similar problems were reported in the coastal part of Croatia, Bosnia and Albania.

Nada Pavicevic, a spokeswoman for Montenegro’s state power distribution company, described the outage as a “disturbance of regional proportion”, and said authorities are still working to determine what happened.

Bosnia’s state power company said that the outage was caused by problems in a regional distribution line, while Albania’s state power company said the “extreme heat” caused the problem.

Montenegro, Croatia and Albania share the Adriatic Sea coastline. Power grids in the region remain connected decades after the Balkan wars in the 1990s.

In the Bosnian capital, Sarajevo, the outage also caused traffic jams, with trams stopping and traffic lights not operating. Similar gridlock was reported in the Adriatic Sea port of Split.

The collapse, which happened just after noon on Friday, came as authorities throughout the region warned citizens to be cautious, drink water and avoid sunshine because of extremely high temperatures.

“Don’t stay in the sun between 11am and 5pm,” warned Serbia’s Public Health Institute in its instructions to citizens. “If you must go out, please take a bottle of water along.”

Meteorologists say the heat in the region this week came from Africa, carrying sand particles that created a cloud-like layer, dimming the skyline.

The sweltering heat was the worst in big cities, where concrete sizzled even in the evening, and where nights offered no real respite as temperatures remained above 20C.

While hot summers are normal in the Balkans, temperatures do not reach such heights in mid-June, prompting weather alerts and warnings.

Earlier this week, authorities in North Macedonia imposed emergency measures until Sunday, after which the heat is expected to relent.

Weather warnings were also issued in neighbouring Croatia, a tourism hot spot, where the heat wave is set to peak on Friday before an expected change of weather on the weekend that could trigger storms.

Montenegrin state television RTCG said that though the citizens of the country’s capital of Podgorica are used to very high temperatures, some complained they have started too early.

Experts say that extreme weather conditions are also triggered by climate change.