What to Wear Running in 40 Degree Weather

Forty degrees is where layering gets simple and a lot of runners feel their best. A long-sleeve top over shorts or light tights is the default, and a short-sleeve shirt with arm sleeves is the same idea with more flexibility. You usually do not need a jacket unless it is windy or wet. Light gloves are the one accessory worth carrying, since hands are slow to warm even when the rest of you is comfortable. Think of the long sleeve as removable insurance: start a touch cool and keep the option to push the sleeves up as you heat through.

The mistake at 40°F is treating it like winter. Tights, a jacket, a hat, and gloves all at once leave most runners overheated within a mile. The whole point of 40 degrees is that your body does the heavy lifting once you are moving, so you only need to bridge the cold first few minutes. The opposite trap is underdressing your hands and heading out in shorts and a singlet on a windy 40-degree day, then spending the first half of the run with stiff, cold fingers. Cover the extremities, keep the core light.

At this temperature, effort decides whether you wear the long sleeve at all. A workout or a brisk run often calls for short sleeves from the start because you will be hot within minutes, while an easy or social-pace run stays comfortable in the long sleeve the whole way. Wind is the variable that flips a perfect 40-degree day into a jacket day, so a thin shell in the back pocket is smart insurance. Humidity is mild here, but a foggy, damp 40 feels cooler on the skin than a dry, sunny 40 at the same number.