Reporting
Dawn Redwoods (Metasequoia)

Dawn Redwoods (Metasequoia) do best in Zones 5 to 8; you might be able to grow them in 4 or 9, depending on conditions. (Wisconsin ranges from Zones 3 to 5.) They do not like cold temperatures, with about -15F the coldest they can tolerate for longer periods. A severe cold snap of -50F may likely have caused damage, depending on how long that temperature lasted, how sheltered a spot your tree is in, your tree's overall health (young trees may be more susceptible), and whether there was any winter protection (burlap, mulch, etc.), or even snow cover (which insulates), that may have protected parts of it. Only time will tell--wait several months into the growing season to see any signs.

Cold damage may show up as twigs and branches blackening and dying back from the tip down; depending on the severity of damage (how many branches were affected, and how much along their lengths, for example), the tree might recover from this, especially if the roots were protected. You might ask a local garden nursery for their thoughts about your tree and the cold snap that you've experienced. They can recommend a proper approach for care during the growing season to help the plant recover. Good luck! Dawn redwoods are beautiful trees.