Spatial and Temporal Evolution of Urban Heat Islands in a Warm Sub Humid City (2019–2024): The Guadalajara Metropolitan Area, Mexico

The rapid growth of the Guadalajara Metropolitan Area (GMA), Jalisco, Mexico, has caused the urban heat island effect to increase its average annual temperature year after year, with record maximum temperatures recently recorded during the spring, specially in 2023 and 2024. This context motivates the present study, which analyzes the spatial and temporal evolution of the heat island effect in order to identify patterns and trends that can inform decision-making to mitigate the long-term adverse effects in specific areas of the study region. The approach is quantitative, using descriptive statistics, vector calculus tools and the thermal gradient analysis. Maximum temperature data were obtained from the ERA5-Land reanalysis and were adjusted in Python based on the National Meteorological Service (SMN) meteorological station database. The ERA5-Land data were bias-adjusted using station data to strengthen methodological transparency. The results show an increase in the average maximum temperature over the last 6 years in most of the GMA, with a trend toward an increase in the average monthly minimum temperature of ≈0.1°C per year in the municipalities of Guadalajara and Tlaquepaque, and ≈0.5°C/year in Tonalá. The heat island effect was concentrated in the south and east of Guadalajara, areas with the highest population density and the lowest density of green space per inhabitant. All of the above highlights the need to strengthen the mitigation strategies that have been implemented in the study area to reduce the development of the urban heat island effect, especially in the south and east of Guadalajara.