leg warmth

I have a pair of green spyder pants that i love but they”re more like a shell and underneath that i have baselayer pants, Kombi, that are level 3 warmth which is something in the middle in warmth. So when i go riding here (east coast) it gets very cold, especially up north and I need a solution. Do i get new pants or is there something i can wear over the baselayers for added warmth.