This jacket keeps me warm in low 30s to low 40s with a long sleeve base layer, and works fine on its own or with a light base layer up into the low 50's. Above that, you might start running a little hot...The Windstopper fabric provides great insulation on blustery days, and insulates well in rain, even after the material starts to absorb water (it's initially mildly water repellent, but will gradually soak up moisture in constant/heavy rain). The fit is trim in the trunk, but not restrictive in the shoulders; the jacket offers good range of motion for my arms and trunk without excess material flapping in the wind. One minor gripe for me is the small rear pockets--i.e., they provide enough space for wallet, tube, gels, but little more room if you have to strip off warmers, hats, etc. during a progressively warmer ride. Overall, this is top-notch jacket for fall, early spring, and possibly winter rides (depending on where you live). I liked my first jacket so much that I bought a second one, and I've been wearing them 2-3 days/week since early October.