Ulster who could have knocked Munster off the top of the Magners League with victory over the Dragons, have also had to call off their game against the Welsh region with a frozen pitch at Ravenhill.
Under-soil heating has enabled both matches scheduled to take place in Wales to go ahead. The Scarlets host last season's Grand Finalists Leinster while Edinburgh travel down to play the champions Ospreys in Swansea.
The Scottish side haven't escaped completely from the conditions as they have been forced to draw up congintency plans after the closure of Edinburgh airport earlier this week.
Munster take on third-placed Cardiff Blues on Saturday and the kick-off time at Thomond Park has been brought forward to 17:00hours.
The weather has also caused changes to the match officials for this weekend's action.
Scarlets v Leinster Nigel Owens (WRU)
Munster v Cardiff Blues - Alain Rolland (IRFU)
Ospreys v Edinburgh - James Jones (WRU)
With the 12 Magners League sides heading into a fortnight of European action after this weekend the festive period derby fixtures are now the next league game for six of the sides.
On Christmas eve Aironi and Benetton Treviso meet for the first time before a reversal of the fixture on New Years eve.
Connacht host Munster and the Ospreys face the Scarlets on Boxing day.
There are three games on Monday December 27, an all Scottish affair in Glasgow, the Dragons play the Blues and Leinster travel to Ulster.
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