Tens of thousands of people braved the rain — and a couple of severe storms — to be part of the fourth annual Northern Spark. Despite the downpour, the all-night arts festival lit up venues across Minneapolis. Presented by Northern Lights.mn, a nonprofit arts organization, the event’s mission is to expand our artful use of public spaces. At the opening ceremonies (which were quickly moved inside the Convention Center), Minneapolis Mayor Betsy Hodges led the kick off the celebration. Drum ensemble Mu Daiko and all-female rap group GRRRL PRTY rocked the crowd, who then went out into the night to explore the giant video projections, temporary street installations and experimental performances.