In California it is quite normal for houses that have their air conditioning turned down to have condensation on the outside.
Due to cold conditions inside and humid air outside.
As a child I frequently had frozen condensation on the inside of my bedroom windows due to high humidity inside and freezing cold outside.
Its not a problem.
As a matter of interest next time its very cold and frosty, check your window sills to see if the frost has melted close to the windows - showing heat escaping through the inside sills and window frames .