@nprofile1q... polyester is ok for repelling water, but it's a terrible insulator and doesn't allow your skin to breathe, so you just get itchy and sweaty despite not actually being warm. Look for 100% wool instead! Ideally a wool overcoat - the length works against both rain and wind and wool is so good that you don't even need a thick/heavy one.

It's even better for bedding because it regulates rather than just cooks. So a wool duvet is good all year round, cooling you in summer and warming in winter.