Foggy windows are common in areas that have weather colder then 35 degrees Fahrenheit and in areas near the ocean. Most people assume that foggy windows occur mostly due to cold weather.  However, when you live in an area near the beach such as Newport or Laguna, foggy windows can occur when the weather heats up too.

Fog in the air happens when moist air from the ocean is cooled.  In Southern California this often occurs when warm moist air blowing in from the ocean meets cooler temperatures on land.  There must be some kind of particle in the air for the moisture to adhere to in order to form fog as well.  A particle can be salt or a pollutant.  Waves crashing on the beach cause salt particles to be dispersed into the air creating the perfect particle for the ocean moisture to cling to.  Salt allows fog to form with very low humidity levels.

When this ocean created fog rolls into land it lands on everything, including your windows.  If your windows have any seal leakage the fog will condense on the inside of the double pane window, creating and leaving a fogged window addition to foggy weather.