CLO expresses the thermal insulation a clothing ensemble provides against heat transfer from the body to the environment. 1 clo = 0.155 m²·K/W. A higher value generally means more insulation, although air permeability, fit, movement and moisture change real-world performance.

Approximate values for individual garments can be combined to estimate an outfit’s insulation. This is useful for comparison, not a laboratory measurement: air trapped between layers and garments compressing one another affect the total.

There is no universal coat threshold. For low-intensity everyday use, many people benefit from a light or medium coat below 10°C, with greater insulation becoming useful below about 5°C. Between 10 and 15°C, a trench, overshirt or thin jacket is usually more adaptable.

Wind, rain and long exposure can move your coat threshold upward. Walking in calm sunshine may let you dress lighter at the same air temperature. Start with an easy-to-remove layer and adjust from experience.

Three light functions are more adaptable than one heavy piece: a base that manages moisture, a light sweater or sweatshirt for warmth, and an outer layer that limits wind. Remove the shell first, then the mid-layer as you warm up.

At 10°C, a long sleeve, light knit and trench are a solid starting point. Around 12–13°C, reduce the knit or shell depending on conditions. Near 15°C, a tee with a cardigan or overshirt offers flexible everyday comfort.

15–17°C is transition weather: pair a short-sleeve base with a cardigan, overshirt or thin jacket. At 17°C, a portable layer can handle cool mornings and evenings while a single top may work in midday sun.

From 18°C toward 20°C, try a light shirt, tee or thin long sleeve with jeans, chinos, a skirt or dress. Carry a thin layer if you will sit in shade, remain inactive or return late.

At 20–21°C, a thin overshirt or cardigan helps in the evening, wind or air conditioning. Above 22°C, an outdoor jacket is often unnecessary and breathable tops with light bottoms tend to feel more balanced.

At 25°C, a heavy jacket can add excessive insulation. A thin packable layer still makes sense if your day includes strongly air-conditioned interiors.

The temperature–CLO bands in this chart are DRAEVA approximate CLO reference ranges designed for everyday decisions. They are not direct outdoor-temperature prescriptions from ANSI/ASHRAE 55, ISO 7730 or ISO 9920, and they do not reproduce copyrighted standards tables.

ASHRAE methodology includes a dynamic clothing-insulation estimate based on prior outdoor temperature to model outdoor adaptation among occupants of mechanically conditioned indoor spaces. It is not a ‘wear this CLO outside at this temperature’ rule. This guide combines thermal-comfort and clothing-insulation concepts, limited typical outfit examples and practical layering principles in original wording.