Long-Term Assessment of UHI and SUHI in Modena: Integrating Landsat Land Surface Temperature and Meteorological Observations

The urban heat island (UHI) refers to higher air temperatures (Tair) in urban areas than in surrounding rural environments, while the surface urban heat island (SUHI) describes analogous differences in land surface temperature (LST). This study presents a long-term assessment of UHI and SUHI in Modena, Italy, combining meteorological Tair observations with Landsat-derived LST from 188 daytime and 19 nighttime summer scenes (1985–2023). Four indicators—magnitude and range 1 of overall thermal variability and magnitude and range 2 of urban–rural thermal excess—were applied in parallel to LST and Tair to characterize the intensity and spatial variability of thermal conditions within a consistent daytime/nighttime framework. Results indicate significant long-term increases in summer LST, with daytime warming rates of 0.26 °C yr−1 (urban) and 0.27 °C yr−1 (rural). Daytime urban–rural LST differences ranged from 4 to 6 °C; nighttime differences were smaller (1–3 °C). Daytime Tair urban–rural differences were weak and not statistically significant, whereas nighttime Tair showed a clearer urban warming signal. Nighttime LST correlated more closely with Tair (r = 0.49–0.52 across indicators) than daytime LST, and nighttime LST showed strong correlations with Tair in both urban and rural areas (r = 0.96–0.98). Daytime imagery better captures SUHI spatial intensity, whereas nighttime observations provide a more consistent surface-to-atmosphere thermal link, highlighting the value of integrating satellite LST with in situ Tair for integrated UHI and SUHI assessment in medium-sized cities.