December is a great time to take a vacation to somewhere warm if you don't like the winter. I like to travel to the Canary Islands from end of December to January. Last time we had 20-25 degrees. Definitely warm enough for the beach.
On 1st January, London gets 8 hours of daylight, Edinburgh 7 hours, Stockholm 6 hours. Tenerife has nearly 11!
By February it's almost spring, there's hope, light at the end of the tunnel. I agree with GP that Dec/Jan is a great time to get away from northern Europe.