California summer temperatures (1970-2004) were analyzed by use of data from 273 NWS cooperative observer sites. Temperature trends from a subset of about 80 stations were further analyzed over two coastal areas: San Francisco Bay Area (SFBA) and South Coast Air Basin (SCoAB). Summer nighttime minimum temperatures in the two basins showed expected greenhouse gas induced warming, while corresponding daytime maximum values showed a concurrent warming in inland areas and cooling in low elevation coastal areas influenced by marine air penetration. This suggests that regional-warming in inland areas resulted in increased sea breeze activity. Dew point temperature trends at the NWS sites at coastal San Francisco airport and inland Sacramento airport showed a larger rate of increase at the coastal site. In addition, changes in the vertical profiles of temperature, wind speed, and dew point temperatures at the NWS rawinsonde sites at Oakland and San Diego were also analyzed. The goal of this investigation is increased knowledge of global warming impacts on California coastal areas, as coastal cooling could impact summer daytime ozone levels, water supply, fossil-fuel use, agricultural production, and human thermal-stress levels.