Less packs of people during the winter?

So it's mid-December and I'm noticing that there are less packs of 3-10 people cycling around San Diego.  During the Spring, Summer and Fall there are a lot of small packs that I see cycling up and down the coast or even inland.  With December now it full swing I still see those weekly group rides with 20-30 people speeding through Encinitas but I don't see a lot of the smaller groups.  Interesting phenomenon.  I blame it on the light fog.  Who wants to end up better rear-ended by a car while cycling down Pacific Coast Highway?