There are several things you can do, however, to prevent your feet from suffering too much in the wintery conditions.
OvershoesAs the name suggests, overshoes are simply an insulated, waterproof covering that goes over your cycling shoes, while leaving any clipless mechanism free to engage with the pedal. One of the best ways to prevent cold feet, is to avoid getting them wet. This can be easier said than done if you are cycling through fallen snow or rain; overshoes, however, do a decent job of keeping the water out.
There are several different types of overshoes. Some are made from neoprene and provide good insulation and are almost completely waterproof; however they are slightly bulky. Another type are more like elasticated socks; these are fine for keeping the wind out and will deflect any surface water, but are not so good if you want to go out in heavy rain.
SocksWith the outside of the shoe fixed, it is time to look on the inside. People often put on the biggest, thickest socks that they can find in an effort to keep warm; unfortunately, this often has the opposite of the desired affect. The thick socks fill out the shoe and leave no air between the shoe and the foot to act as insulation. Even worse, they can at times restrict the blood flow to the feet, resulting in the inevitable cold.
Thin socks also have their problems. The clipless mechanism on cycling shoes is a big heat sink; it is basically a bit of ice cold metal covered perhaps by a thin insole. If you only wear thin socks, then that heat sink will be in almost direct contact with your foot for the duration of the ride.
Ideally, therefore, you want to combine the best of both kinds of sock - the ostensible warmth of thick socks, with the size of thin socks. Seal skin socks can offer this kind of compromise, as can other synthetic alternatives; however, these can be prohibitively expensive if you want to buy several pairs. Another option is to choose slighlty bigger cycling shoes than you would normally opt for; you can then wear thick socks while leaving room for circulation of both blood and air around your feet.
Cling FilmSome professional cyclists and many amateurs swear by wrapping their feet in cling film before going out on a cold winter's day. The advantages to this are the potential waterproofing and windproofing effects. The downside, however, which may well counteract any benefits, is that cling film will make your feet sweat. Now, we are not particularly bothered about having smelly feet while cycling, but, as we have already mentioned, allowing your feet to get wet is a surefire way to suffer from cold feet quickly.
The LegsSome cyclists prefer to wear cycling shorts all year round; their legs are moving and feel fairly warm, so they see no need to wear full length cycling trousers. This can, however, be a cause of cold feet. Although the legs move during cycling and may not feel ostensibly cold; unless you are climbing hills, the calves have a relatively limited amount of movement.
In winter, your calves will become cold. There are not a great deal of nerves in this area, so they will not feel especially uncomfortable; the down side though, is that the blood that passes through the calves will also cool down. By the time it reaches the feet, it will have lost some of its potential to keep the feet warm, and the feet certainly have enough nerve endings to make you know about it!
We highly recommend cycling in the winter, it can be even more peaceful and enjoyable than summer if you are well prepared. If, however, the cold weather is too much for you, perhaps you could consider a cycling holiday to warmer shores such as Tenerife or Mallorca.