The greater the difference between the temperature and dewpoint temperature the lower the relative humidity at the location of the observation. The ocean is the largest source of water vapor. Dew Points in Calif are usually in the 5O's as compared to the Gulf Coast, for instance, which is usually around 70 degrees. It turns out that the dewpoint temperature in coastal areas is generally the same as the temperature of the ocean from which the air passes. Thus, dewpoint temeperatures along the California coast are generally in the 50s and along the Gulf Coast in the 70s.
Relative humidity relates to condensation.