I have Raynaud's - quite badly in winter, and even sometimes in summer.
In my case, it appears to be connected with the Alpha-1 Antitrypsin Deficiency I have (it's a genetic thing). Some (about 33%) A1ATD sufferers have excessive Angiotensin Converting Enzyme in their muscles, which leads to exercise induced hypertension; quite dramatic in my case (see threads regarding Good Friday, 2014).
Upshot is, I'm really prone to painful, "dead" hands when exercising, and especially when cold and wet. We've had tense moments on the tandem in the past, when riding in cold rain, and I couldn't operate the brakes or gears.