Not because of slippery roads, etc. but just due to the colder weather. During the summer I had no trouble cruizing at 18 mph on the flat with no wind, but now that temps have dropped to 40s F I find myself pushing to stay above 16. I'm not talking maximum effort, just cruising speed. I've also noticed that my legs feel stiff and rubbery (if that makes sense) rather than just tired or sore after a long ride.
I'm dressing adequately so that I neither feel cold nor sweat excessively and I'm staying hydrated even though I'm not as thirsty.
Is this just part of riding in the cold?