Italy placed all of its major cities under the highest heat alert Thursday as a blistering heat wave gripped .

The heat has set a national temperature record in Austria, fueled wildfires in France and disrupted energy and transport systems across the continent. Temperatures have climbed to above 104 degrees Fahrenheit in several countries, prompting health warnings for millions of people.

Italy's health ministry placed all 27 cities it monitors under its national heat surveillance system on red alert Thursday — the first time this year the entire network has been under the highest warning level simultaneously. The alerts stretch from Trieste in the northeast to Palermo in Sicily and signal a health risk for the entire population.

Residents and tourists were urged to avoid direct sunlight during the hottest hours of the day, remain inside when possible and drink plenty of water. Adjustments were made at major tourist attractions, with evening opening hours extended at landmarks like Rome's Colosseum and Pantheon.

Cooling mist fans have been installed at the Colosseum's entrances and additional medical stations have been made available.

The most intense temperatures were recorded in Austria, where the mercury reached 106.2 degrees Fahrenheit on Wednesday in the village of Bad Deutsch-Altenburg near the Slovak border, according to GeoSphere Austria. It was the highest temperature ever recorded in the country.

Austria is also facing severe drought. Rainfall from Jan. 1 through June 30 was 27% below the long-term average nationwide, while some eastern regions received only half their normal precipitation. Climatologist Alexander Orlik said some parts of the country had not experienced such dry conditions since 1885.

In Hungary, prolonged drought and on the Danube River have severely affected the country's only nuclear power plant, which relies on river water to cool its reactors. Plant operators have reduced output to about 10% of normal production, prompting the government to introduce emergency conservation measures.

On normal days, the 44-year-old Soviet-designed facility generates roughly 50% of the country's electricity.

"Several factors will determine whether Hungary's most important power plant can avoid a complete shutdown in the coming days," said Hungarian Prime Minister Péter Magyar, visiting the site Tuesday, attempting to balance reality while projecting optimism.

Germany also faced growing concerns over the impact of drought on transportation and industry as water levels on the Rhine and other rivers continued to fall. Transport Minister Steffen Bilger warned Thursday that low water levels posed major challenges for inland waterway shipping, industry and the broader logistics chain.

In southeastern France, firefighters maintained a large presence in the Var region after authorities said a major wildfire there was no longer spreading but remained capable of reigniting. The blaze, which began July 20, has burned more than 23 square miles, making it the largest recorded in the region in recent decades.