Pavlovas don't normally come to mind in the winter since they are generally regarded as a summer dessert.  I always questioned the sense in that though?  High humidity is the serial murderer of pavlovas.  Sure there are other factors that could undermine your pavlova, such as whites contaminated with yolks or grease / water in the mixing bowl, but I assert that weather is public enemy number one since it is not a factor you get to control.