When finally it is warm and sunny after a long winter, it's tempting to dress as if it is summer. But with the transitional weather in March and April, this is also the time of the year a lot of people tend to get sick. After all, 50-60°F is not really that balmy. And even with the kinder temperatures, Spring (in New England at least) tends to be windy - and the wind hits cyclists directly in the face and chest with more force than it does pedestrians.
It took me a while to find a comfortable balance dressing for Spring's faux warmth, but after a couple of years I've more or less settled on a system. The trick for me is to keep it light, but windproof in the torso and to keep my neck covered. I find windbreakers too casual for everyday wear, and I also tend to sweat in them. But I like lightweight wool blazers and thin (unlined) trench coats. They are breathable, and the fabric is dense enough to protect from the wind without being too heavy.
My eyes are sensitive to the sun and wind, and Spring brings a powerful mixture of both. On the bike, my sunglasses pretty much stay on most of the time and I smear moisturiser or vaseline around my eyes on windy days.
As far as keeping my neck covered, lightweight silk scarves work well once big wool scarves get too warm and bulky. They also fold up very small if it gets too hot for them in the middle of the day. Recently a friend introduced me to the amazing world of inexpensive "cowboy" scarves. She has a collection of silk scarves in every colour and pattern imaginable, and she buys them from these online cowboy stores for like $20 each. Done!
Dressing for work on the bike can be tricky in the springtime, and of course different strategies will work for different people. I don't like being too hot or too cold, but I also don't want to stuff my pannier with pounds of "just in case" layers when I leave the house, so I like a system without too much bulk. What's your method of dressing for transitional weather?