2024 saw a record-breaking number of dangerously hot and humid days

As the planet heats up, the atmosphere is holding more moisture – and this is resulting in more days with weather conditions close to the limits of survivability

The planet experienced a record number of dangerously hot, humid days in 2024 as climate change increases global humidity to unprecedented levels.

The global average number of high humid heat days over land exceeded the 1991-2020 average by 35.6 days last year, 9.5 days more than the previous record set in 2023, according to the State of the Climate report 2024 published by the American Meteorological Society.

In hot, humid conditions, people struggle to cool down, as the moist air smothers the evaporative cooling effect of sweating. This makes such weather extremely hazardous to human health, says Kate Willett at the UK Met Office, who worked on the report. “Your body starts to really struggle to offload heat, and so it can be really dangerous,” she says.

Cover photo: Shanghai saw many days of extreme heat and humidity in 2024