Urban Heat Island (UHI) is an increase in temperatures inside urban areas compared to areas outside the city, affecting human health and energy consumption. UHI is usually measured by the difference in air temperature (A-UHI) or surface temperature (S-UHI). Cairo, Egypt’s capital is a big city with a hot arid climate. Its metropolitan region hosts 20 million people on 1471 km<sup>2</sup> area (2021), so UHI is expected in such a mega city, but UHI in Cairo was not studied much and it is not fully covered in literature. This paper aims at proving the existence of SUHI in Cairo, measuring its spatial and temporal characteristics, and demonstrating the phenomena of anisotropic SUHI in Cairo. The research methodology utilizes remote sensing data for surface temperature, using (MODIS thermal images from 2000 to 2021). Urban characteristics are modeled using urban GIS data and MODIS Land cover data, then GIS raster analysis is used for the statistical assessment of Land Surface Temperature. Key findings indicate that nighttime average surface temperature in Cairo’s urban area was hotter than non-urban surroundings by 2.4℃, with the max of 5℃ in city center, during July (2000-2005). SUHI increased to 3.8℃ with the max of 7.5℃ in (2016-2021). The area of hotspots increased from 359 to 530 km<sup>2</sup> in the same period. This increase can be correlated with rapid urban growth. The area of Cairo has almost tripled during this period (585 to 1471 km<sup>2</sup>). The daytime SUHI in Cairo is Anisotropic. Most world cities are surrounded by greens (Forests, Farms, etc.) where the temperatures are lower than urban areas, both day and night, desert cities are cooler than desert surroundings during daytime (Inverted Heat Island). Cairo has non-uniform surroundings, with desert to the east and west, and farmland to the north and south. During daytime, Cairo’s urban area is cooler than the desert but hotter than farmlands. It is important to take this phenomenon into consideration when studying UHI in Cairo and similar cities. Averaging of surroundings’ temperatures can be misinterpreted as there is no daytime SUHI.