During MVMCP, the fireworks are at 9:30 p.m., and the second showing of the Christmas Parade is at 10:45, with snow on Main Street during the parade and after. I'm not sure if it was continuously snowing through the whole party or not, but I believe it was. Hope that helps.
Last year when we got to MK around 1 in the morning on Dec 30, it was snowing on Main Street. The park was closing for day guest, but still open for hotel guests. When we left around 4 am it was again snowing on Main Street. It was also snowing on Main Street after the park closed on New Year's Eve as we were leaving. I thought they just did this while guest were leaving. There was no snow when we left after Magic Hours this year, but it was not the holiday season.