I've been running in temperatures as cold as 32 degrees in just tights/leggings with a little fleece lining in them (gear designed for cold weather activities). I picked them up for $25-30 a pair at Target (the C9 line).
Hope that helps!
Camp Good Grief 5k 2012 - 31:50
Gobble Wobble 5k 2012 - 30:00
Turkey Trot 4 Mile Race 2012 - 38:38
Ugly Sweater 5k Fun Run 2012 - 27:19
Move-It Memphis 10K 2013 - 55:36
Germantown Half Marathon - 2:08:53
FedEx St. Jude Classic Fairway 5k - 4/13/2013
Pittsburgh Half-Marathon - 5/5/2013