California summer temperatures (1970-2004) were analyzed by use of data from 273 NWS cooperative observer sites by Bornstein et al. (submitted, this conference). Summer nighttime minimum temperatures showed expected greenhouse gas induced warming, while corresponding daytime maximum values showed concurrent warming in inland areas and cooling in the coastal areas of the San Francisco Bay Area (SFBA) influenced by marine air penetration. This suggests that the regional-warming of inland areas resulted in increased sea breeze activity. The Regional Atmospheric Modeling System (RAMS) was used to test this hypothesis for the SFBA. Nested simulations, with a horizontal grid resolution of 4 km on its innermost grid, were carried out with pre-European influence and 1992 land-use conditions for the month of July. Results were in agreement with the above mentioned observations, i.e., during sea breeze hours, near-surface temperatures increased in the eastern half of the Central Valley and decreased in its western half and throughout the SFBA. Sea breeze wind speeds were increased within the Carquinez Straight, the only sea level passage from the SFBA into the Central Valley. Coastal cooling could impact summer daytime ozone levels, water supply, fossil-fuel use, agricultural production, and human thermal-stress levels.