Weather is always an important consideration when planning a trip to Pioneer Cabin. Weather in Sun Valley (elevation 6,000 or so) is relevant since the trailheads are just above that elevation. But the cabin itself is at a much higher elevation. More specifically, the point forecast for Pioneer Cabin from NOAA is available here. There may also be recent beta about trail conditions on the facebook page. The National Resources Conservation Service maintains a weather station in the vicinity at 7,620' elevation which can provide further trail information, including temperatures recorded and snow depth.
There are a number of routes to Pioneer Cabin and all have various advantages and disadvantages. Regardless of the trail one chooses, there are three main trailhead parking areas.
The blue waypoints on the map indicate the "three-season" parking locations before and after the roads have been cleared of snow. Trails can easily be seen by zooming in on the satellite base map (including the very crowded Corral Creek parking lot).
The red waypoint marker on the map indicates the winter trailhead nearest the cabin which uses a route I've plotted up Button Creek, or rather on the ridgeline directly to the east of Button Creek. Some friends and I made this trek in March 2016 to watch the spring equinox full moon arrive over Hyndman Peak. The track is below.