Summer has just begun in the Northern Hemisphere but a brutal heat wave is already gripping parts of Europe, China and the United States, where record temperatures expected this weekend are a stark illustration of the dangers of a warming climate. Extreme heat advisories have been issued for more than 100 million Americans with the National Weather Service forecasting particularly dangerous conditions in Arizona, California, Nevada and Texas. Several European countries, including France, Germany, Italy, Spain and Poland, are also baking in searing temperatures. Greece said its top tourist attraction, the Acropolis, would close during the hottest hours on Friday as temperatures were expected to reach 40 degrees Celsius (104 degrees Fahrenheit) in Athens. The mercury may soar as high as 48C (118.4F) on the islands of Sicily and Sardinia, the European Space Agency said — “potentially the hottest temperatures ever recorded in Europe.” North Africa has also been sweltering and Morocco’s meteorological service issued an extreme heat red alert for southern parts of the country. Some regions of China, including the capital Beijing, are experiencing soaring temperatures and a major Chinese power company said its single-day power generation hit a record high on Monday. Parts of eastern Japan are also expected to reach 38 to 39C (100.4 to 102.2F) on Sunday and Monday, with Japan’s meteorological agency warning temperatures could reach previous records. Last month was already the hottest June on record, according to the US space agency NASA and the European Union’s Copernicus Climate Change Service. Extreme weather resulting from a warming climate is “unfortunately becoming the new normal,” warns Secretary-General Petteri Taalas of the World Meteorological Organization (WMO). Excessive heat is one of the deadliest meteorological events, according to the WMO. One recent study estimates over 61,000 people died from heat during Europe’s record-breaking summer last year.