| PET (˚C) | Thermal Impression | Degree of physiological stress |
| <4.0 | Very cold | Extreme cold stress |
| 4.1 - 8.0 | Cold | Strong cold stress |
| 8.1 - 13.0 | Cool | Moderate cold stress |
| 13.1 - 18.0 | Slightly cool | Slightly cold stress |
| 18.1 - 23.0 | Neutral (comfortable) | No thermal stress |
| 23.1 - 29.0 | Slightly warm | Slightly heat stress |
| 29.1 - 35.0 | Warm | Moderate heat stress |
| 35.1 - 41.0 | Hot | Strong heat stress |
| 41> | Very hot | Extreme heat stress |