If the group is very slow (if they try to take two long rests over the course of the adventure), the druids move forward with their plan.
The group wakes up from their second long rest and they notice the storm has moved. The storm used to be over the town of Freehaven; now it's closer to the river and several miles south, pretty close to Cedar Valley except on the Federation side of the river. The storm is getting bigger! What's going on over there?
The group heads south and finds a druid circle -- there are several stone henges, and there's an altar in the center. In the center of the circle are all the surviving druids, performing a ritual over the Orb. It looks like they're unleashing its power against the village of Cedar Valley!
The characters will need to attack the druids and then calm the storm. The druids are guarded by werewolves. The Orb is shooting lightning up into the Storm, and is visible even through the rain; the group probably sees the druids before the druids see them. The group will need to plan an ambush and then defeat all enemies. Climbing trees to avoid werewolves might factor heavily into the plan. If the battle seems too easy, narrate that the werewolves are trying to jump or climb into the trees. (Or, perhaps, to knock the trees down!)