Due to urban sprawl in densely populated areas, more populations are now migrating toward high-altitude areas of northern part of Pakistan. Abbottabad and Mansehra districts are one of the most populated areas of Pakistan with an altitude >1000 m. In this paper, three indices were used to determine urbanization's impact on the environment in high-altitude areas. Land Surface Temperature (LST), Heat Island Magnitude (HIM), Normalized Difference Built-up Index (NDBI), and Normalized Difference Vegetation Index (NDVI) are calculated on the selected area using Google Earth Engine. Landsat and MODIS are used to calculate three indices for the period 2001–2020. LST and MODIS daytime readings are used, and the results showed a strong correlation between LST and NDBI, while the correlation between LST and NDVI is weak compared to the prior one. After calculating all three indices the time series figures were plotted to observe the extreme values in the data which were then flattened out by applying the running average. The northern part has snow cover due to which all three indices have negative values in spatial distribution pattern, while the southern part of both the districts has more urbanization due to which high LST >20 °C and NDBI values > 0 were recorded while NDVI values were near to 0. It is noted that urban heat island values increased in 2011–2020 as compared to 2001–2010. So, the built-up index showed high values in 2001 as urbanization rapidly increased but the LST value was low and NDVI values were high. 2001 urbanization sprawl has a bigger impact in the next years as NDVI values decreased in urban areas and LST values increased.