Since days are much shorter in the cold season, the
rides greatly depend on the artificial light. If you
don't use a lamp, then it can often happen that you
can't even ride a bike, since you came late from work.
And then there are only weekends left.
There are two types of bike lights. The ones mounted
on the handlebar and the other ones, mounted on the
helmet. They both have their advantages and
disadvantages. The handlebar type is good since the
light beam is not parallel to your sight and therefore
you can see shadows that help you recognize the terrain
configuration much better. But you can point the light
beam only in the direction of the bike, which is not
helpful in tight corners, singletracks and also if you
want to look away from the trail or down on your bike.
And the last but not least, because the light is on the
handlebar and thus in front of the bike computer and any
other gadgets that you might use, you can't really use
them as if it was daylight. And on the other hand, the
light mounted on the helmet has got just the opposite
characteristics and thus more good ones than bad ones.
The fact is that for normal off-road riding you need
fairly powerful light, which is as bright as the car
headlights! But unfortunately they don't come cheap.
You also need rear red light and reflecting elements,
if you ride through urban areas.
In those gray days it is nice to wear yellow glasses
to make them more colorful and to recognize the terrain
So, get yourself equipped for the cold days and don't
let them keep you away from your bike and your trails.