Multi Decadal Surface Temperature Trends in Riyadh (1985-2024): Seasonal Patterns and Urban Heat Island Amplification

Abstract

Rapid urbanization combined with regional climate change is intensifying heat exposure in arid cities, yet long-term assessments remain limited. This study presents a comprehensive multi-decadal analysis of near-surface air temperature in Riyadh, Saudi Arabia, covering the period 1985-2024. Monthly temperature records were aggregated into annual mean, maximum, and minimum indices and evaluated using linear regression and the non-parametric Mann-Kendall test with Sen’s slope estimation to ensure robust trend detection. Results reveal a persistent and statistically significant warming signal across all temporal scales. Annual mean temperature increased at a rate of 0.59˚C per decade (p ≪ 0.01), with minimum temperatures rising faster than maxima. The stronger increase in nighttime temperatures indicates asymmetric warming consistent with enhanced nocturnal heat retention. Warming is evident in nearly all months, with particularly strong trends during spring and summer. Comparison across sub-periods shows a stepwise increase in mean temperature, confirming a sustained long-term shift. The observed patterns align with regional greenhouse-gas-driven warming while also reflecting urban-scale influences such as land-cover change, reduced evapotranspiration, and increased heat storage in built surfaces. Although the study does not explicitly separate urban and rural signals, the structure of the trends is consistent with known urban heat island mechanisms. These findings establish a robust empirical baseline for understanding long-term warming in a rapidly expanding desert metropolis. The results carry important implications for heat risk, energy demand, and urban sustainability, highlighting the need for climate-sensitive urban planning and heat-mitigation strategies. The study also underscores the value of sustained long-term observations for supporting climate adaptation in arid urban environments.