Due to consistent urban expansion, cities of developing countries like India are witnessing significant alteration in their thermal environment. This study aims to investigate the impact urbanization induced green and blue space changes on land surface temperature (LST) surface urban heat island intensity (SUHII) in Darbhanga city during 1991–2021. Landsat datasets have been utilized for mapping urban expansion and changes in green and blue spaces. The violin diagrams have been used to examine the variation and distribution of SUHII over different LULC types. The result shows that Darbhanga city have witnessed very fast urban expansion mostly in terms of built-up area expansion (about 238%) over open land, crop land and dense vegetation. The analysis of LST and SUHII shows that both LST and SUHII is increasing in Darbhanga. The minimum and maximum LST in city has increased by about 0.66 °C and 1.04 °C, respectively during 1991–2021. The area under very high SUHII category have significantly increased from 0.18% to 0.38% area of the city during three decades which may have significant impacts on thermal comfort of the city. The violin diagrams shows that built-up area high SUHII during all study years with median SUHII values increasing, describing that built-up expansion raises the SUHII in cities. On the other hand, water bodies and dense vegetation have consistent low SUHII, describing their role in mitigation of SUHII and LST. Study may assist city planning bodies and other agencies in dealing with the rising SUHII and LST in cities.