New Meteorological Analysis Shows Heat Season Extends 214 Days Per City

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

CITY	COUNTRY	FIRST	LAST	SEASON LENGHT
Hassi Messaoud	Algeria	Jan 09	Nov 07	303
Cairo	Egypt	Jan 21	Dec 03	317
Agadir	Morocco	Feb 02	Nov 28	300
Timbuktu	Mali	Jan 01	Dec 31	365
Navrongo	Ghana	Jan 01	Dec 31	365
Lagos	Nigeria	Jul 01	Sep 27	278
Luanda	Angola	May 29	Oct 13	168
Conakry	Guinea	Jun 10	Sep 23	261
Cape Town	South Africa	May 16	Nov 15	181
Bloemfontein	South Africa	Mar 21	Sep 27	176
Nairobi	Kenya	Jul 15	Mar 15	123

CENTRAL AND NORTHERN ASIA

CITY	COUNTRY	FIRST	LAST	SEASON LENGHT
Zarafshan	Uzbekistan	Apr 13	Sep 26	167
Astana	Kazakhstan	May 24	Sep 06	106
Yakutsk	Russia	Jun 21	Jul 29	39
Ulaanbaatar	Mongolia	May 15	Aug 15	93

CENTRAL AND SOUTH AMERICA

Mexico City	Mexico	Apr 17	Jun 19	64
Bogotá	Colombia	Apr 08	Aug 29	144
Monterrey	Mexico	Jan 30	Nov 27	302
Manaus	Brazil	Jan 01	Dec 31	365
Rio de Janeiro	Brazil	Jan 01	Dec 31	365
San Salvador	El Salvador	Jan 01	Dec 31	365
Merida	Mexico	Jan 01	Dec 31	365
Asunción	Paraguay	Jan 01	Dec 31	365
Buenos Aires	Argentina	Oct 28	Mar 14	137
Campina Grande	Brazil	Sep 22	Mar 27	187

EAST ASIA

CITY	COUNTRY	FIRST	LAST	SEASON LENGHT
Shanghai	China	Apr 11	Oct 03	176
Beijing	China	May 01	Sep 08	131
Yinchuan	China	Jun 24	Aug 02	35
Seoul	Korea	Jun 19	Sep 20	94
Tokyo	Japan	Jun 16	Sep 22	99
Hong Kong	China	Apr 15	Oct 15	184

EUROPE

CITY	COUNTRY	FIRST	LAST	SEASON LENGHT
London	England	Jul 18	Aug 13	27
Moscow	Russia	Jun 22	Jul 14	23
Madrid	Spain	May 19	Sep 14	119
Athens	Greece	May 17	Oct 08	145
Lisbon	Portugal	May 27	Oct 09	136
Paris	France	Jun 16	Sep 16	93
Munich	Germany	Jun 19	Aug 22	35
Tiranë	Albania	May 15	Oct 04	143
Warsaw	Poland	Jun 22	Aug 18	58
Stockholm	Sweden			0

MIDDLE EAST

MIDDLE EAST

CITY	COUNTRY	FIRST	LAST	SEASON LENGHT
Abadan	Iran	Mar 18	Nov 13