Do these wine taverns close in the winter? What does the colder weather do to them?
Check individual websites to see which heurigen are open - plenty are open. Instead of sitting outside, you sit inside.
All the bigger and well-known Heurigen have usually ample space inside (bearing a license as a restaurant) and will be open.
The strictly traditional Heurigen (just having a Heurigen license) are open during the warm season at certain weeks, only.
When are you going to be in Vienna? I checked the town website for the town we stayed in a few years ago. They list 40 heuringeren and their daily calendar for the next month lists between 9-14 of them will be open each day. Many of these had lovely decorations and a fireplace or wood stove so I can imagine they are quite nice on a cold winter’s evening.
@mona: No plans to go to Vienna any time soon. However, it's a town we will revisit, and probably in late fall/early winter.
@Paul What’s the name of the town you’ll be revisiting? Our interesting town on the SW side of Vienna and bordering the Wienerwald is Perchtoldsdorf. .