Final answer:
An early observable sign of a chilled puppy can include behavioral changes like restlessness or lethargy, as well as physical signs like shivering and a hunched posture.
Step-by-step explanation:
One of the first observable signs of a chilled puppy includes a change in behavior, such as restlessness or lethargy, which may suggest discomfort due to cold temperatures. Additionally, physical signs could include shivering, a hunched posture, or a reluctance to move, which are efforts by the puppy to conserve heat. These observable signs should prompt immediate action to warm the puppy and prevent further decline in temperature, which could lead to hypothermia, a potentially life-threatening condition.