Cloth weight matters most. Fabrics of around 230–260 grams feel noticeably lighter and more breathable than winter cloths.
The weave also makes a big difference. Breathable weaves let air circulate, reducing that stuffy feeling after a full day of wear.
As for colour, light shades such as beige, light grey and pale blue absorb less heat than dark tones. We recommend visiting the atelier to feel the cloth before deciding.