Riding in the winter can be a big help to summer ridding, odd you may think but you become more aware af what is going on around you, you constantly watch the road surface for changes in colour, fluids etc, your lines & riding style will be smoother, throttle control etc will be smoother, ability to react to changing road conditions is faster & smoother, but above all else self preservation will make you a better rider.
Having had to do long & short distances when I was in the forces & only had a bike to get home on, doing 200 odd miles from portsmouth to lincoln WHAT ever the weather, summer or winter, snow etc,etc gives you the best training in bike control you can get.
Chris.