The exceptional heat, driven in part by a warming climate, has exacerbated extreme weather events around the world, including wildfires, heat waves and dangerous flooding.
A global map shows where average daily temperatures from June 1 to Sept. 23 were warmer or cooler than average based on a 1979-2000 average. Much of North America was warmer than average, with some areas — including northern Canada, the southwest U.S. and northern Mexico, showing temperatures more than 6 degrees Fahrenheit (3.3 degrees Celsius) above average.
Hot, dry and windy conditions fueled an early and intense wildfire season in Canada that, by mid-July, had already become the country’s worst on record. Much of the wider Arctic region experienced warmer-than-normal temperatures that accelerated ice melt.
The global map spins and focuses on the Arctic region, most of which was warmer than average. Some areas, including northern Canada and some of Greenland, show temperatures more than 6 degrees Fahrenheit (3.3 degrees Celsius) above average.
In many places, the heat persisted for days and days on end. Phoenix saw 31 straight days at or exceeding 110 degrees Fahrenheit, and a total of 55 days above that mark from June through Sept. 23.
The global map spins and focuses on the Southwest region of the United States, which shows much warmer temperatures than normal. Phoenix, which is known for its extreme heat, shows temperatures more than 2 degrees Fahrenheit (1.1 degrees Celsius) above average.
El Paso faced 44 consecutive days above 100 degrees Fahrenheit, beginning in the middle of June. The punishing heat in the borderlands between Texas and Mexico became deadly for some migrants on their journey to the United States, officials said.
The global map spins and focuses on the United States-Mexico border region. A large swath of southern and western Texas, as well as northern Mexico, experienced temperatures more than 6 degrees Fahrenheit (3.3 degrees Celsius) above average.
Parts of the southeastern United States like Louisiana also sweltered under seemingly endless hotter-than-normal days, accompanied by high humidity that made the air feel swampy and suffocating.
The global map spins and focuses on the southeastern region of the United States. Parts of Louisiana, like Baton Rouge, show temperatures more than 4 degrees Fahrenheit above average.
One of the year’s most unusual heat waves happened in the middle of South America’s winter. Temperatures in parts of the Chilean Andes soared to more than 20 degrees Fahrenheit above normal during a heat wave in late July and early August.
The global map spins to South America, where average daily temperatures were higher than normal for much of the continent. Temperatures in parts of the Chilean Andes were more than 8 degrees Fahrenheit (4.4 degrees Celsius) higher than normal, with much of Paraguay with average temperatures more than 6 degrees Fahrenheit (3.3 degrees Celsius) above normal.
Europe saw wave after wave of blistering heat that rolled across the region for an exhausting four months, as firefighters battled blazes in Croatia, Switzerland and across the Mediterranean.
The globe spins to Europe, where countries stretching from Spain to Romania show average temperatures more than 4 degrees Fahrenheit (2.2 degrees Celsius) higher than normal.
Even in the Middle East — which has come to expect hot summers — the unrelenting heat, combined with high humidity and parched conditions, made it dangerous to do daily tasks. In Africa, large swaths of Sudan, South Sudan and the Democratic Republic of Congo were much warmer than normal.
The map spins to focus on northeastern Africa and the Middle East. Areas of Sudan and Ethiopia show temperatures greater than 6 degrees Fahrenheit (3.3 degrees Celsius) higher than normal.
The heat was particularly pronounced in northwestern China, where the dry desert climate regularly makes it one of the hottest parts of the country. In the city of Turpan, temperatures reached nearly 120 degrees Fahrenheit in mid-July.
The globe spins to focus on northern China and Mongolia, where a large area shows temperatures more than 4 degrees higher than normal since June.
Japan endured its hottest summer on record, according to the country’s weather agency. In large cities like Tokyo, the urban heat island effect can amplify heat and trap it overnight.
The globe spins to Japan, where the northern part of the country shows temperatures more than 4 to 6 degrees Fahrenheit higher than normal.