I usually don't bathe mine unless it's at least 60 degrees and sunny. You could shampoo their manes and tails, now, though. I'm doing Norman's pretty soon, and the weather is the same here. I can't stand dry, brittle manes and tails.
I know how you feel! I get so impatient and I'm dying to give my mare a bath, but its just too cold right now still. Lol. Do you have a metal shedding blade? That and a curry comb work awesome. Just keep brushing and brushing. It kills your arms, but it helps.