You do not have to have an oncoming weather system to have clouds form in your area.
Local conditions can cause thunderheads and other cloud types to occur.
For example, in Florida, residents can expect brief but often intense afternoon thunderstorms almost daily between April and September. This is due to humid, unstable Caribbean, Gulf of Mexico, and moist subtropical Atlantic air moving into the heat rising off the land. The atmosphere can't hold all this energy, so it dumps it off in the form of a daily thundershower. Still, clouds are a good indicator of weather to come. The fourth category of clouds, those that have vertical development such as cumulus and cumulonimbus, is a renegade group that operates under special rules.