It only happens once in a blue moon...
On Saturday, May 18th a blue moon will begin rising over Boston at 7:52pm, with the sunset will occurring at 8:01pm. The moon rises in the east, so you're going to want to look that way. If you're trying to grab photos, go somewhere facing east with a picturesque foreground. Two well-known spots to watch a Boston moonrise are North Point Park
in Cambridge and the BU Bridge
on the Boston/Cambridge line.
Photo by @thebostoncal on Instagram: