Europe, the world's fastest-warming continent, has been ravaged by record-breaking heat and destructive wildfires this summer, with France and Spain particularly hard hit in recent weeks.
The focus of the heatwave has since moved further east, with temperatures in Austria hitting successive national records this week, peaking at 41.2C on Wednesday.
Italy is accustomed to hot summers, but the red alert issued by the health ministry stretches from Palermo on the southern island of Sicily to Bolzano in the mountainous north.
Such a warning indicates a potential health emergency with prolonged high temperatures posing a serious health risk to the entire population.
With rivers at historic lows, the region of Piedmont, centred on the city of Turin, declared a state of emergency this week for drought and the risk of wildfire.
Hungary has switched off decorative and non-essential lighting at all state institutions, including its parliament, most of the Buda Castle and Chain Bridge, at night to save energy.
Record-low water levels on the Danube have forced the country to largely shut down its sole nuclear plant, which uses the river for cooling, stretching power supply capacity to its limits.
Romania was preparing to sink four rock-filled barges into the Danube to divert water to its only working reactor and buy a few more days of operation.
The authorities in the capital Bucharest have dimmed the intensity of street lights by a third and switched off lighting at night at landmark buildings and museums to save power.
Low water levels are causing problems for shipping on the Rhine in Germany, where many vessels can sail only part-loaded, raising freight costs.
The river is an important shipping route for commodities such as grains, minerals, coal and oil products.
In Bosnia, tourists have taken shelter in the constantly cool temperatures of the UNESCO-listed Vjetrenica cave to escape outside temperatures of 40C.
Vjetrenica is in the south of Bosnia and Herzegovina, about 25km north of the Adriatic town of Dubrovnik, where cruise liners arrive daily with thousands of visitors.
Numbers allowed to visit the cave are limited because of the sensitivity of the environment.
Its constant 11C temperature year-round has made it a refuge for biodiversity as well as for humans.
