The sun seems to hide most days and the skies are often gray. On the other hand, city is less busy – apart from the holidays.
The disadvantage is that weather can be very cold. This is the time to visit markets and join the New Years’ crowds celebrating in the streets, and it is a time for concert and opera lovers. Winter in Prague is very charming when snow covers all the historical buildings, and the Lesser Town looks like something from a fairy tale. However, you have to be lucky to see the city like this (usually snow comes in January and February and a white Christmas is rare). Most tourist attractions have reduced opening hours, but are still open. Also keep in mind that it will get dark early – around 4:00 pm in December and January and around 5:00 pm in February. For winter you have to pack warm clothing and shoes which will protect you in the freezing days when temperatures can go below 0°C (and some days can go as low as -25°C).
Consider bringing a very warm jacket, gloves, winter hat, warm socks and very warm winter shoes.