The winter urban heat island: Impacts on cold-related mortality in a highly urbanized European region for present and future climate

Helen Macintyre*, Clare Heaviside, Xiaoming Cai, Revati Phalkey

*Corresponding author for this work

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Exposure to heat has a range of potential negative impacts on human health; hot weather may exacerbate cardiovascular and respiratory illness or lead to heat stroke and death. Urban populations are at increased risk due to the Urban Heat Island (UHI) effect (higher urban temperatures compared with rural ones). This has led to extensive investigation of the summertime UHI and its effects, whereas far less research focuses on the wintertime UHI. Exposure to low temperature also leads to a range of illnesses, and in fact, in the UK, annual cold-related mortality outweighs heat-related mortality. It is not clearly understood to what extent the wintertime UHI may protect against cold related mortality. In this study we quantify the UHI intensity in wintertime for a heavily urbanized UK region (West Midlands, including Birmingham) using a regional weather model, and for the first time, use a health impact assessment (HIA) to estimate the associated impact on cold-related mortality. We show that the population-weighted mean winter UHI intensity was +2.3 °C in Birmingham city center, and comparable with that of summer. Our results suggest a potential protective effect of the wintertime UHI, equivalent to 266 cold-related deaths avoided (~15% of total cold-related mortality over ~11 weeks). When including the impacts of climate change, our results suggest that the number of heat-related deaths associated with the summer UHI will increase from 96 (in 2006) to 221 in the 2080s, based on the RCP8.5 emissions pathway. The protective effect of the wintertime UHI is projected to increase only slightly from 266 cold-related deaths avoided in 2009 to 280 avoided in the 2080s. The different effects of the UHI in winter and summer should be considered when assessing interventions in the built environment for reducing summer urban heat, and our results suggest that the future burden of temperature-related mortality associated with the UHI is likely to increase in summer relative to winter.

Original languageEnglish
Article number106530
JournalEnvironment International
Early online date23 Apr 2021
Publication statusPublished - Sept 2021

Bibliographical note

Funding Information: The research was funded by the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Environmental Change and Health at the London School of Hygiene and Tropical Medicine in partnership with Public Health England (PHE), and in collaboration with the University of Exeter, University College London, and the Met Office. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, the Department of Health or Public Health England. We also acknowledge data access provided by ONS, the Open Government Licence for UKCP18 data accessed via the Met Office user interface, and the Centre for Environmental Data Analysis (CEDA) web portal used to access MIDAS data. CH is supported by a NERC fellowship (NE/R01440X/1) and acknowledges funding for the HEROIC project (216035/Z/19/Z) from the Wellcome Trust.

Open Access: This is an open access article under the CC BY license (

Publisher Copyright: © 2021 The Authors. Published by Elsevier Ltd.

Citation: Macintyre, Helen L., et al. "The winter urban heat island: Impacts on cold-related mortality in a highly urbanized European region for present and future climate." Environment International 154 (2021): 106530.



  • Climate change
  • Temperature exposure
  • UHI
  • Urban health
  • WRF


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