Cold weather riding can be rough on the hands.
While this may not work for everyone or on every type of bike, it was a quick, easy & cheap solution that has gotten me through two winters.
Materials used:

old hoodie, sweatshirt or jacket with stretchy elastic at wrist.
duct tape with the design of your choosing
Tape measure
Scissors

Step 1: Cut Material

Measure the length of your handlebar from center outward.
Measure same distance on sleeve. Include the wrist elastic.
Cut sleeves.

Step 2: Tape Outside of Sleeve

The duct tape is meant to block the wind, rain and snow.

Do not tape over the wrist elastic.
Feel free to make stripes or designs with colored tape.

Step 3: Tape the Cut End of Sleeve

Fold a small margin of tape over the cut end so it does not fray or unravel.
(You could sew it if so inclined but not necessary. )
The sleeve lining will keep your hands warm.

Step 4: Stretch Over the Handle Bars

the wrist elastic should stretch over the brake levers and shifter,
And close of the wind from the center.
you should have enough room for hands to use brakes and so forth.
Happy riding.