I went to Wal-mart and bought a thick lined pair of those nylon  snow or ski pants with a bib that covers the chest. Water proof and I can ride in almost freezing weather and my legs and chest stay nice and warm. The material is soft enough they will just slide over your work clothes and come off in a sec. I think they cost about $25 and up for thicker lining, but worth it.  With a good coat you should stay nice and warm.  I bought a bunch of those dollar store hand warmers and slide one inside of my full face helmet so the back of my neck stays warm. I guess you could tape one to the top to keep the head warm.     If it's real cold like in the high 30's, low 40's I stick a small rubber hot water bottle down the bib under my coat. Then I am almost too warm. Plus, you can always stop and make your self some hot chocolate!  

My low temp cut off point is 10F on sunny days, 30F if it is damp out.

You need to go get some polypropylene liner socks, long john pants and a long john shirt. Then swing by Cycle Gear and pick up a proper motorcycling balaclava design to work with full face helmets, and some boot rain covers. Military surplus shop should have German Army motorcycle dispatch rider winter mittens.

I like riding in the cold, the bike runs better. You just have to check the tire pressure more frequently. And at stoplights, grab the cylinder, the leather won't burn and transfers just enough heat to keep your fingers warm.

Other side of the scale, if it is in the mid 80s or higher and I don't have a liquid cooled primary bike, I don't ride. It gets hot enough here that Harleys, V-Stars, Savages and related seize up.

Went on a modest trip last week at 44F with the sun out.  I wore some leather Army gloves with wool liners and doubled up on socks.  A windshield and helmet made it all tolerable but I started getting cold after about 30 minutes.  On the return trip it was about 52F and that was much better.  I think my new cut off point will be about 50 degrees if I will be doing highway speeds.  Around town 40F is OK.

When I was a kid I sometimes rode while it was snowing but a bike was the only transportation I had so there wasn't much choice.  When you are young the blood pumps around the body a little better.