Extreme Heat Trending Upwards across Major Global Cities


 
In 43 major world cities, the number of extremely hot days increased by 72% between 2000 and 2024. The International Institute for Environment and Development (IIED), which published the study, judges +35c as extreme heat. Comparing individual years can exaggerate change, but a rising trend is clear when comparing the periods of 1994-2003 and 2015-2024, which, as the IIED notes, saw a 26% rise in the number of days of extreme heat.

Number of days of extreme heat (+35c) in 43 major world cities. (2000-2024)
Source: International Institute for Environment and Development, ‘World’s major cities hit by a quarter more hot days than in the 1990s'. (2025)





Note: The city selection includes the world’s 40 largest capital cities by population and three additional politically significant cities. The selection is global in reach, including: 16 cities in Asia-Pacific; 12 in Africa; 8 in the Americas; and 7 in Europe.

Nine cities in the study recorded their highest number of extremely hot days in 2024, which included Rome, Tokyo and Washington DC. According to the International Labour Organisation (ILO), at 33-34c, workers operating at moderate intensity already lose half of their labour capacity.

See more:  
See more...Access Temperature Data on World Economics
See more...See IIED source report



More perspectives using World Economics data

South and Southeast Asia Bear the Brunt of Rising Extreme Heat
South and Southeast Asia Bear the Brunt of Rising Extreme Heat
From 1994-2003 there were 4,755 days of excessive heat , defined as 35c+, across the world’s twenty most populous capital cities. That has now grown to nearly 6,500 days in the most recent decade. The densely-populated capitals of South, Southeast and West Asia have predominately experienced this increasing heat stress . Based on a linear annual trendline across these three decades, the number o...
Global South Governance Declines
Global South Governance Declines
The Governance ratings of 84 countries of the 100 listed as constituting the Global South declined on the World Economics Governance Index over the last decade. This reflects falling standards across data reflecting corruption, rule of law, press freedom and political rights. Note: Definition of Global South by World Economics is used. As can be seen in the chart above there has been a...
When China Rules the World
When China Rules the World
Chinese GDP will be more than double that of the US in just over a decade, if recent growth rates persist. Economic activity in China is almost certainly already around 54% larger than in the USA. Few investment portfolios, business plans or government calculations reflect the large and growing dominance of Chinese economic activity, mostly because of the inappropriate use of market prices to assess ...