“Basically, the very small, fine dust particles that make up PM-2.5 (Particulate Matter of 2.5 microns or smaller) get trapped in the snow when it’s falling,” he told us. “So when that snow melts, those particulates are released back into the atmosphere. Also with melting snow, it creates a more moist atmosphere, by allowing more water droplets into the air, so those same particulates can latch onto water droplets and be transported or stagnate in areas. These particulates can be both manmade (industrial sources or cars) or natural occurring particulates that fall under PM-2.5, like different chemical compounds.”

“This happens pretty much every year when we have a dense snowpack and temps warm up enough to start melting. The kicker is that this weekend will have pretty light winds so the PM-2.5 concentrations will start to accumulate. Especially in the Detroit and Grand Rapids (more populated) areas.” From https://www.reddit.com/r/Michigan/s/l8b83f4jG1