There is always the possibility that other factors would be critical to the exact answer to this question.  Such as material grade, process, applicable code.

But, overall, I see no reason a weld could not be stopped, let sit over the Holiday break, and then restarted.  Obviously, Pre-heat, weld pass cleaning, and other factors would have to be dealt with before striking the arc and continuing with the weld. 

Welds can sit even longer than that.  But, as stated, there may be other factors contributing to an extended period of work stoppage.

The main concern would be the wording of the WPS, especially on some pipe and on special materials.  There will be time periods for how long it takes to complete a pass and how long between passes.  And as you haven't given us any of that, only you can tell.

Then, you say in was unavoidable.  It may take contact with the engineer to get approval for continuing the work. 

Have a Great Day,  Brent

I've seen this addressed in the job specs many times, but am not able at this moment to give section/paragraph etc reference to a code.
"Industry Standards" dictate a root and hot pass must be deposited on pipe before abandoning the weld. Procedures often will give a specified depth of deposition, minimum ambient temp or heat maintained etc.
Curiously enough, tacked together is usually OK. I'm assuming the assumption is that any cracked tacks would be removed prior to welding.
Welders like this rule because it gives them the chance to not get in a hurry any where close to quitting time.

AND, I have seen where incomplete welds were removed due to violation of the abandonment.