dress like winter. Can't tell you how many times I've been out early spring and froze my ass off. Thermals/under armor is a good bet, warm boots and socks are also. Rain gear will keep you dry, as well as block the wind.
Good advice Ted! I bought a new "Real" rain suit this year, actually spending a little money, some new heavy duty long johns and some 15" rubber boots. Nothing worse than being cold and wet while fishing. Not for this fisherman anymore.
Actually, there IS something worse. Capsizing and being ill dressed, because you could easily die from hypothermia. That's why I recommend a pair of breathable waders (with belt) and a dry top. Hope for the best, plan for the worst.