North face 500 fill puffer jacket. If you can, go with the variety that has a hood (could be the 700 fill but I'm guessing here). Its gotten me through 5 years of walking every day in the dead of frozen winter (far below 0).

Then, during the summer you can send it back to them where it will get re-fillled, patched or replaced depending on what you need. However after all this time all that mine needs is a bit of a restuff but even without it it's still incredibly warm. The lifetime warranty is incredible