About 1.1 billion people in Asia, Africa and Latin America are at risk due to a lack of sufficient refrigeration to keep food and medicines safe, as well as their personal temperature.
The statistics come from a study by the UN into the impact of global warming in 52 countries, with more than half of those affected living in slums of cities.
The UN’s health agency has also warned heat stress linked to climate change will likely lead to 38,000 extra deaths a year between 2030 and 2050.