Peaceable Projects Inc. is a U.S.-based non-profit group that brings the vast resources of the wide world together with the ongoing needs of the people who live, work, and travel on the Camino de Santiago pilgrim trail network in Spain.
I started on the 6 March in Pamplona, as I was told that the Pyrenees might be to risky to cross because of the snow.
Throughout the whole of March I had perfect walking conditions with only 2 or 3 days of rain. Most of the time I walked in t-shirts, but of course you will need a jacket and a fleeze for the mornings. Also the big advantage is that it's not so crowded, I never had any problems to get a bed in the albergues. I had a light-weight sleeping bag (750gr) with me, for the really cold nights you always can ask the hospitalero for a blanket.
When I crossed the Cebreiro it was sunny and warm, though 3 days later I saw on the Spanish TV that it was snowing again and Pilgrims walking through the snow, so you never really know and you will need to be prepared.
After all, I still believe that March is the best month for the Camino, not so crowded and not too hot, and the best of all - you walk into the spring!