Hi Hazem.  It's an example of what we call an "absolute phrase" (the noun and participle form their own phrase).  

Another way of expressing the same idea is: "if the weather permits, we may drive to the beach".

Other examples of an absolute phrases are: "God willing, we'll be able to travel next year", "having got up, we ate our breakfast", or "the temperature being warm, we decided to go for a picnic".

Sometimes there is a conditional element to these phrases, but sometimes they just express a completed action.  Often they link two separate ideas in a sentence.

I hope this makes sense!