My understanding is that the term 'next weekend' is ambiguous unless given context.
As Nino said, if you refer to 'this weekend' then you are referring to the coming weekend (on a weekday) or the current weekend (if in it). If you use the term 'next weekend' in this context it will refer to the weekend after 'this weekend'.
However, if you just use the term 'next weekend', logically you are referring to the coming weekend. That is the plain meaning of 'next'.
So the safest way is to give a date...
