The quickest weather online giving an idea of the intensity of the rain over the next few days is mountain weather. This also has temperature predictions for the height of the Loser itself at 1838m - fortuitously this is about 20m below top camp at Steinbruckhohle.
Perhaps better is the Austrian forecast for Bad Aussee - for the day and the next week.
Local weather forecasts appear on the radio (in German, of course). In the winter, snow reports can be found (we presume). There is a local forecast on the Bad Aussee tourist office site, https://www.badaussee.at/. You can phone for a forecast (also in German) or you can try the Tourist Office in Bad Aussee (no idea if they post a bulletin in the window - we don't seem to have tried).
But for an up to the minute (maybe) idea of the weather right now, see the Grundlsee Photo of the Day or try the Loser WebCams - giving current views of several places around the Loser ski area. Caution! These could induce an irresistible desire to drop everything and travel to Austria immediately!
See Flood-Risk Caves for places to be aware of.