Geological / environmental event
The festival of Greengrass occurred late in 1491; dark magics were afoot.
The festival of Greengrass is celebrated through much of the Forgotten Realms. In Ambershandy, it is celebrated with a fair in the Main Street, with festivities starting at dawn when the sun crests between the twin mountains of the Thunderpeaks. However this year, the sun never made that ascent, and winter looked set to continue...