* * * WARMTH * * *
I bought this jacket for New York weather. I got to wear it in 25-50°F weather with ONLY a base layer and was warm the whole time despite wind, no sun, light flurries in the air and descending. On the warmer days with sun I was the perfect temperature thanks to the breathable nature of the fabric. I can't wait to try this jacket out in the southern California weather on those cooler mornings. Note: I did NOT try this in rainy weather and I probably wouldn't because it's not actually waterproof.
* * * SIZING * * *
This is where stuff gets wonky. I ordered a S even though my measurements were for a XS since I always have sizing issues with cycling clothing. Once trying it on I regretted not going with the sizing chart and buying the XS so I overnight shipped the XS. The XS fit perfectly in the body but like almost every other jacket/jersey, etc. that is women's specific... the shoulders were TOO narrow. I have a very slim chest and torso and normal sized shoulders for my height (5'7) so this was to be expected and I ended up just keeping the S. Overall I'd say read the sizing chart. The jacket is true to size and I could have definitely comfortably fit a couple layers under the XS sans the shoulder situation.