Be prepared for moderate temperatures during the day, and cool nights. I've switched from trousers to shorts for when I'm at home, but I wear a t-shirt and a sweatshirt or a sleeved shirt over it, at this time of the year.
Monday it was around 60, sunny, with a light breeze. The temperature dropped to the low 50s from Tuesday through yesterday. Today, we're socked in with rain, temperatures are in the low 40s. As Zach mentions, there still can be snow here in the area. After all, the change in seasons is not like flipping a light switch, for as much as the popular culture seems to think it is. Days are getting longer, true, and gradually, we're pointing ever closer to the Sun. But the ground is still relatively cold. Also, you want to prepare for the occasional rain. We had thunderstorms roll through very early this morning, as the front rolled in.
