Young children are vulnerable to extreme temperatures due to their physiological and anatomical characteristics and behavioural dependability. The latter is a relatively unexplored area. Therefore, the current study investigated the skin temperature as a proxy of the thermal state of children and care providers in day-care centers, the ability of the care providers to estimate the thermal state of the children and their knowledge on this topic. Results from 104 children (<four years old) and 58 care providers recruited from six different day-care centers in winter and summer in the Netherlands show that there was no difference in thermal state between the children and care providers. A significant relation (p < 0.05) was found between skin temperature of the care providers and thermal sensation in winter and summer, but not for the skin temperature of the children and the assessed thermal sensation score of the children by the care providers (p > 0.05). Furthermore, many care providers had difficulties naming symptoms of heat illness and the care providers with ≤5 years work experience had a lower knowledge level of thermoregulation than care providers with >5 years work experience. It is recommended to train care providers in thermal assessment, in particular novice care providers that have less knowledge on this topic.