All of the above. In colder weather, I always wear a base layer and have several different thicknesses to choose from, depending on how cold it is. If the weather is dry and cool, a long-sleeve jersey is sufficient over the base layer. If it gets a little colder and still dry, I wear a vest over the jersey. If there is rain or any threat of it, I wear a rain jacket over the base layer -- without a jersey unless it is really cold (less than 20 F). If the weather is cold (less than 35 F), I wear a jacket or rain jacket over the base layer, again with no jersey unless it's really cold.