Riding throughout the year is a challenge for many reasons, but clothing is certainly one of the trickiest. We have always been told that layers are the way to go, and for riding, particularly year round riding, this couldn't hold more true. Unfortunately, when we go to our motorcycle oriented shops, we are presented with a lot of top layer options, but almost nothing when it comes to suitable base layers. When it comes to dealing with temperatures, it all starts with what you are wearing closest to the skin.
Pro athletes have known this for years, and have had access to gear that has only become widely available to the consumer in the last few years. We probably know it best by the brand image of UnderArmour, but good moisture wicking compression style gear is available from many companies, and ranges in price from $10 to well over $100, depending upon your needs. Good base layers apply to all four seasons too, with some providing warmth and others working to more efficiently cool. There are added benefits as well. Recent studies in the sports world show benefits from the compression gear in terms of reducing muscle fatigue and improving recovery, in addition to the protection from the elements.
So let us look at specific cases.
During the winter months, morning temps below freezing, with afternoon temps in the low to mid 40's. I still need to dress office casual for work, so it becomes all about the foundation layers, and form fitting is the order of the day as it fits under clothing with minimal impact. The big name here is of course UnderArmour. In their ColdGear offerings, you can get a good quality product that will keep you warm, while working well under your clothes, but most importantly, not cooking you while you are indoors working during the day.
Personally, I prefer the mock turtleneck styles, as they work well under a dress shirt. These are excellent products, and are widely available. If you have access to a good running store, you may be able to find better products that will keep you warmer, but this stuff is available from pretty much any sporting goods store in the country. As temperatures rise into the summer, I still go base layers, but switching to products that are suited to dealing with the problem of moisture and cooling. Again, compression, but utilizing products geared towards the summer workout. Again, we will use the UnderArmor product line, simply because of it's broad availability. The HeatGeat products offer compression short sleeve or tank styles, mixed with shorts (or pants) that help minimize the moisture issues.
You can find competitive products from many companies, including Nike, New Balance, & Brooks, and there are other companies that specialize in similar products, including CW-X, Orca, and 2XU. Of these, the company I buy most of my stuff from is 180s, with their QuantumHeat/QuantumCool products. Then of course there is the bargain stuff, Walmart, Kohl's and Target all carry products that compete at low prices, but the best of the bargain stuff that I have found is the Academy Sports house brand, BCG, however, stock can be very hit or miss.
Add to these basics, good socks, a balaclava and good glove liners, and you have a foundation that I have worn quite comfortably in temperatures well below freezing when paired with well planned outer layers.
The main thing to keep in mind is that you are dressing for comfort. These base layers provide you that warmth or cooling you need so that your mid layer is what you are wearing to work, with your outer layer being your crash protection gear.