The weather is colder in the winter in central CA, but not near as cold as the snowy places elsewhere. I feel fortunate that I can ride all year round. Lately, it has been in the low 40's in the morning at the start, but warms up to the mid 50's by noon. With the sun out and the right clothes, it is fine.

You need full gloves, tights, and an insulated biking jacket or some layers. Once I start riding (since there are a lot of hills) I get warmer. If it were overcast and cold, it would probably feel too cold. Anyway, once I drag myself out there, it always feels worth it by the time I get back.

So, it might be worth getting out there even if it is below 60. If it gets below freezing, then it's time for the trainer or the gym....