Again, I have to disagree with Ric Stern.

Everyone I know who has begun weight training in the winter has made big gains in the season following. They didn't lift for mass, they used very low weights and very high reps - but it helped in every case I know of. One friend in particular, a female professional mountain bike racer, began lifting a few years ago in the winters and promptly began posting her best results, after she turned 40. She has been a coach for about 10 years and now insists all her clients lift.

Placebo effect? Good for only certain athletes? Quite possibly either one. But that doesn't matter if results follow. I haven't lifted since before I started cycling (it bores me), but I am planning to this winter. I'll let you know if I see any improvement from it.