The clothes you wear in the field are very important. They are not about fashion but about survival and comfort. Dress appropriately, and be prepared for a change in weather.
The best way to deal with extremes in weather is to dress in layers. The layer next to your skin should be a material, like polypropylene, that wicks away moisture if you begin to sweat. Keeping the cloth next to your skin dry is key to staying warm. The layers above that should be for insulation and warmth; they do this by trapping air. Wool or synthetic materials like fleece are best for this layer because these materials retain some warmth even when wet. The top layer should be some type of water-repellent and/or wind-resistant material. Cotton clothing won’t keep you warm if it gets wet, so be very careful about wearing denim jeans, cotton sweatshirts, and cotton socks when hunting. Be sure to bring along a warm hat!