Leslie - Some seeds require cold stratification for a certain amount of time (Penstemons can take 8 weeks to 4 months of cold per JL Hudson
http://www.jlhudsonseeds.net/S..., columbines need cold...). My winters have been warmer the last few years so I've been trying to get seed requiring cold into the refrigerator by Nov1st, then I can take them out at the end of Jan and let them acclimate to my remaining winter/spring. Some traded seed may go in later, but I'm trying to just not plant any cold requiring seed after Dec1st. Usually cold stratification means cold and moist (so seed in moist sand, peat, soil mix - in a baggie or your jug). Baggies take less room and you can sprinkle your moist soil plus seed mix onto your jug of soil and water in when you take from the fridge.
I also try to keep my jugs in shade until January as we get some warm days during winter that could cause them to sprout if it in the sun. They'll live through the frosts in the jug but get too big for direct planting out from the jug and I try not to have too many I have to pot up before planting out (my spring is often cold and damp until late - not freezing cold just soil too cool to plant in). I also tend to put much more soil in my jugs than many folks so the early sprouters can live in them longer. Winter sowing does work in the warmer zones - it's just about adjusting your methods.
Some of my wintersowing pics
https://www.gardenweb.com/idea... .