Insulated jackets to keep your temperature up. These jackets, in essence, consist of some kind of warm fluffy stuff sandwiched between two layers of wind-resistant material. Synthetic insulation (usually very fine polyester fibres and under various brand names - Primaloft, CoreLoft, PlumaFill etc.) maintains warmth even when wet, whilst natural goose or duck down offers a higher warmth-to-weight ratio. Whichever you choose, they will usually be warmer than a fleece of equivalent weight.