New Meteorological Analysis Shows Heat Season Extends 214 Days per City

July 3, 2025, London/Lagos — As global temperatures rise, many cities and communities are reeling from the impacts of extreme heat. A new analysis of global cities by Climate Resilience for All’s meteorological team led by Dr. Larry Kalkstein found that on average, that heat season extends for 214 days per city—with extremely hot days happening anytime within that period.

The study evaluated the last five years of meteorological data (2019-2023) from regional and national meteorological services to assess how long the heat seasons extend in 85 cities in all climate zones worldwide, excluding humidity. The analysis identified the earliest and latest day that reached 90°F/32°C at each location during this five-year period – showing the extent of the temperature thresholds in each city.

This analysis further revealed that:

• Heat seasons are not confined to the recognized summer seasons and are much longer in duration.
• 20 of the 85 cities analyzed can have extremely hot days anytime during the year. Tropical cities such as Bangkok, Manila, Singapore and Rio de Janeiro face near year-round heat seasons where 90°F/32°C days can occur anytime during the year.
• Mid-latitude locations such as New York, Melbourne, Berlin, and Buenos Aires have varying lengths of these periods of high temperatures. 
• The Southern Hemisphere locations such as Dhaka, New Delhi, and Cairo show that extremely hot temperatures are likely early and late in the year.

Urban heat is driven by a warming climate, “the heat island effect”, caused by densely built infrastructure and limited green space and rapid urban migration that concentrates people and development in cities.

“Extreme heat is taking a growing and significant toll on people’s health, causing illness and death, disrupting infrastructure, tourism, and work productivity, and straining healthcare systems—among many other impacts.

Cities never designed for heat now face new heat shocks and stresses. Yet, the planning and response measures for heat are either nonexistent or woefully inadequate for the scale of this crisis,” said Kathy Baughman McLeod, CEO of Climate Resilience for All.

“This analysis makes it clear: we can no longer treat heat as just a normal part of summer. The ‘summer season’ many of us once knew is gone. It is imperative that we mainstream awareness and understanding of extreme heat, so that governments, businesses, and employers manage their risks and impacts with the urgency these conditions demand,” added Baughman Mcleod.

A global NGO operating in seven countries, Climate Resilience for All is focused on protecting women and vulnerable communities from extreme heat. CRA has extensive expertise on both the impacts and the solutions to extreme heat. 

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Lengths of 1^st and Last Hot Days Recorded by Region and City
(first and last day of 90°F/32°C temperatures)

AFRICA

CENTRAL AND NORTHERN ASIA

CENTRAL AND SOUTH AMERICA

EAST ASIA

EUROPE

MIDDLE EAST

NORTH AMERICA

OCEANIA

SOUTH/SOUTHEAST ASIA

CONTACTS:

Geraldine Henrich-Koenis, [email protected]

Kelechukwu Iruoma, [email protected]