As far as I know Red Bull Ring is the only track known so far, with two time of day slots with rain. Been following the event this weekend pretty closely and I don't believe other tracks have been seen.
Personally I'm being cautious, setting my expectations low. But my optimist side thinks back, that Red Bull Ring already had rain a couple of months ago at the last live event, so there is hoping for maybe a couple of other tracks as well.
I guess we won't really know for sure until the update hits, and fortunately that is soon!