Rising Nighttime Heat Threatens African Cities, New Global Study Warns

A new global study has revealed that nighttime temperatures are climbing at alarming rates across major cities worldwide including 13 African cities during moist tropical weather and 10 during dry tropical conditions posing a growing health risk to millions.

The findings, released at the COP30 Local Leaders Forum in Rio de Janeiro, show that 83% of the 100 cities analyzed are experiencing increasingly hotter nights during extreme summer weather. The report warns that while global efforts have focused on keeping daytime temperatures within the Paris Agreement’s 1.5°C threshold, nighttime minimums are rising up to 12 times faster than daytime highs in some urban areas.

The study, conducted by Climate Resilience for All, is titled “Extreme Heat and the Shrinking Diurnal Range: A Global Evaluation of Oppressive Air Mass Character and Frequency.” It analyzed 30 years of weather data, from 1994 to 2024, focusing on two of the most dangerous types of heat conditions for human health “dry tropical” (hot and dry) and “moist tropical” (hot and humid) air masses.

Alarming Trends Across African Cities
In Africa, 13 of 15 cities studied showed significant increases in nighttime temperatures during moist tropical weather, while 10 of 14 cities recorded similar increases during dry tropical conditions.

Among the fastest-warming cities were Agadir, Morocco, where nighttime temperatures are climbing by 1°C every 5.6 years, and Cairo, Egypt, rising 1°C every 16.8 years. Other cities experiencing notable decreases in the gap between day and night temperatures include Dakar, Mombasa, Brazzaville, Upington, Abidjan, and Algiers.

The frequency of extreme heat events is also on the rise. Over the past three decades, moist tropical weather patterns in Africa have increased by nearly 49%, while dry tropical conditions have grown by 14%. Globally, moist tropical heat events are up 37%, with cities adding roughly one extra day of extreme humid heat every 2.5 years.

Health and Policy Implications
Experts warn that hotter nights are especially dangerous because they prevent the human body from cooling down, raising the risk of heat exhaustion, dehydration, and cardiovascular stress. Disrupted sleep from heat also hampers recovery from daytime exposure, putting vulnerable populations particularly the elderly, women, and those in poorly ventilated homes at greater risk.

“Before this analysis, we did not know how rapidly nighttime heat has been rising within the most dangerous air masses,” said Dr. Larry Kalkstein, climatologist and Chief Heat Science Advisor at Climate Resilience for All. “It is critical for us to understand how the heat of summer that sends people to the emergency room is shifting, and what we are overlooking when we talk about it.”

Freetown Mayor Yvonne Aki-Sawyerr said the findings mirror the daily realities in many African cities. “Most of our residents lack access to cooling, and women market traders facing extreme heat all day return to homes that are dangerously hot at night,” she said. “This study sounds the alarm on the hidden threat of nighttime temperatures and pushes us toward solutions that protect people.”

Kathy Baughman McLeod, CEO of Climate Resilience for All, urged leaders to broaden their approach to heat management. “We want this analysis to mobilize city and health leaders to urgently broaden their view of what is a 24-hour heat crisis. This research uncovers a critical blind spot in our understanding of extreme heat,” she said.

Call for Action
The report calls for enhanced heat-warning systems that factor in rising nighttime temperatures, as well as public health and urban planning measures that address heat resilience. Current systems, the researchers note, focus too narrowly on daytime highs, underestimating the risks posed by sustained overnight heat.

Story by: Emmanuel Gameli Dovia

   Comments0