A good rule of thumb is that jacket-weather temperatures are anything below 65°F. But Some people may start wearing jackets at lower temperatures than others, depending on their personal comfort and the weather conditions.
hen people wear thick clothes or jackets, the temperature is usually cold. This typically means that the temperature could be around: Below 20°C (68°F) – Mildly cool, where light jackets might be worn. 10°C to 0°C (50°F to 32°F) – Cold enough for thicker jackets. Below 0°C (32°F and below) – Freezing temperatures, requiring heavy winter clothing.