OCP Outerwear

What about when it gets cooler or the weather isn't so "sunny SoCal" anymore?

If it just "cooler" and you're maybe just a little chilled then you are allowed to add a layer underneath your OCPs. Per CAPR 39-1,

7.1.1.10. Optional Undergarments. Optional undergarments are worn in addition to the t shirt/turtleneck.

7.1.1.10.1. Sleep Shirt. The sleep shirt may be worn untucked under the OCP coat. The sleep shirt will not be worn as an outer garment. The sleep shirt will not be visible under the OCP coat except at the neck. The sleep shirt will be coyote brown (Tan 499). No other colors are authorized.
7.1.1.10.2. Thermal Underwear. Tan 499 thermal underwear may be worn under the OCP. Thermal underwear will not be worn as an outer garment. Thermal underwear will not be visible under the OCP trousers and coat except at the neck.

If you can get your hands on a tan colored "waffle" top, nickname for the mid-weight shirt in the Extreme Cold Weather Clothing System (ECWCS), then you're sitting pretty.

The Tan 499 Fleece

This outer wear item is worn overtop of the OCP blouse, as either a stand alone item or as a liner for the OCP pattern parka or Gore-Tex rain jacket. The fleece jacket has Velcro strips for "CIVIL AIR PATROL" and "LAST NAME" tapes along with a Velcro patch for the rank tab (which should be above the name tape on the right side of the jacket). The rank tab is unfortunately, only available through Vanguard; for cadet airman and NCOs its a blank dark blue tab with Velcro backing that you pin a third metal rank insignia onto and then attach to the jacket, for cadet officers and senior members the ranks come embroidered on. 

My head's getting cold!

The Tan 499 fleece beanie is authorized for field wear.