December 1 is more than the start of meteorological winter. It’s also the start of winter parking season in South Milwaukee. Learn more on this page on the South Milwaukee Police Department website.
From the site:
During the period from December 1st to March 31st, no person shall park a vehicle on any street in the City of South Milwaukee between the hours of 3:00 AM and 6:00 AM.
However, vehicles may be parked during such hours if a permit is obtained from the Police Department after the filing of an application and the payment of $20.00 per month permit fee, $17.00 if obtained after the 15th of the month, or $65.00 for a 4-month permit.
Also, don’t forget the even-odd restrictions during the winter: You can only park on the even-numbered side of the street on nights whose calendar date before midnight is even.
You can learn more about how and when to obtain parking permits here.
South Milwaukee Blog 
I think this web page needs to be updated. I tried to get a parking permit for overnight parking on Feb 20, 2011 – and I was told that I would have pay for the full month of February – with only 8 days remaining in the month. I was also informed the monthly rate is $25.00.