It's still winter, as you can see. There's actually enough snow to go cross-country skiing in Lobau even though temperatures again have risen up to and slightly above freezing.
Relatively mild temperatures make the ice treacherous (nobody would dare going ice-skating there even if the ice weren't covered with snow) but apart from that (and, sadly, the grey weather) it's pretty nice wintery. The only drawback is that dogs still roam Lobau national park, and hardly one on its leash as should be the case.