Climbergirl - The Hub Bike Co-op in South Minneapolis has women's group rides, both fast and slow, on Monday nights in the summer. Of course they're over for the season now but here is the text from their event calendar:

Women's rides - Casual and Road
Women's Road Ride-This is a faster-paced road ride of about 15-20 miles at about a 15 mph average speed. We will ride in a single or double pace line on streets and with traffic. The ride will begin and end at 3020 Minnehaha Ave. South in Minneapolis at 6:00 pm, every Monday from April 16th through the end of August.

Women's Casual Ride-This is a causal-paced ride that will use a combination of bike paths and streets. This is suitable for all kinds of bikes (and all kinds of riders!). The ride will begin and end at 3020 Minnehaha Ave. South in Minneapolis at 6:00 pm, every Monday from April 16th through the end of August.

I know what you mean about winter looming (I'm in the Twin Cities too). There are precious few days left!