In the mist of cold temperatures it is obviously not the best time to work in the garden.  It is important to keep off the soil if it is frosty, sticky or wet.   January, provided that the days are fair, can be an excellent time to clear the land, dig over the garden and condition the soil by add plenty of organic matter.  Frost can be be a great soil conditioner, especially for those like me, who have a high amount of clay.  It helps break up clods of earth and makes the ground easier to work. Depending on where you live and weather permitting January can be a time for planting cold crops.  February is a time to really get gardening again.  Let the weather guide you and test your ground with a soil thermometer  first thing in the morning.  When temperatures stay above 45 degrees for a week, it's time to get sowing.

Get together seeds and plan garden.
Winter-dig and apply compost, soft rock phoshate and greensand.
Cover soil with plastic to warm soil for earlier plantings.
Plant fruit trees, bushes and canes.
Plant kale, leeks, onions, broccoli, swiss chard, cabbabe, jerusalem artichokes, shallots.
Sow radishes, broad beans (fava), parsnips.
Apply fertilizer to asparagus beds.
Plant asparagus.
Feed fruit trees, grapes, strawberries, currants and rhubarb with a Phosphate.
Plant artichokes.
Prune Fruit trees.
Tidy and trim climbers.
Prepare grafting material.
Add leaf mould  into flower beds and vegetable gardens.
Spray dormant oil.

All work in the garden should be done on fine days.