My husband and I cruised out of Tenerife on New Year's Eve and visited Lanzarote, Maderia, Agadir etc. The weather wasn't too good and the seas were rough - the week before we went, they replaced all the china plates with paper ones! There had also been some people who couldn't stand the rough seas and got off the ship in Lanzarote. We definitely wouldn't do this route again at that time of year.
We live in Tenerife, and the sea is the Atlantic . .it changes. the previous answer managed to have a cruise in bad weather . .that is not to say that it will always be rough. We have done that crise twice, both in Winter, and have had calm seas. However, in the Mediterranean at Christmas the week after we sailed, the same ship was hit by a 17 metrre wave and and was left drifiting in very heavy seas for hours. It's the luck of the draw, but usually you'll feel it much less on larger ships. Weather in the Canary Islands at Chrismtas is usually good . .people swim and sunbathe . . but again, it could be cool. Never cold! Have a great time. Valerie.