Urban environmental conditions are strongly dependent on the land use and land cover properties. Urban and rural areas normally exhibit obvious difference in land surface temperature (LST). The Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua (PM satellite) MYD11A1 temperature products (daily and 1 km spatial resolution) for the period from June 1 to September 30 between 2002 and 2008 were used to screen the existence of urban heat island (UHI) phenomena for the city of San Antonio, TX. 8-day MYD11A2 temperature products between 2002 and 2008 were also retrieved to map the temperature climatology at the 1:30 a.m. for the region. The UHI effect was detected in both satellite surface-temperature and meteorological station air-temperature record. The existence of an UHI of the San Antonio downtown area was clearly shown in about 90% of the available cloud-free (or cloudless) data from June 1-September 30 each year. It is especially prevalent in the night-time imagery due to less cloud contamination. During nighttime, the heat island (HI) is about 4 - 5 °K (6 - 8 °F) higher than the average temperature of the study area and 6 - 7 °K (8 - 12 °F) higher than the rural area. Surprisingly, the HI phenomenon is found not only in the downtown area, but also several other small areas in the northern corner. Finally, the long-term UHI effect of San Antonio and its relationship with normalized difference vegetation index (NDVI) were discussed. USGS rainfall data were also used to discuss the possible connections between the UHI and several local storm events.