Soft and wearable electronics for monitoring health in hot outdoor environments are highly desirable due to their effectiveness in safeguarding individuals against escalating heat-related illnesses associated with global climate change. However, traditional wearable devices have limitations when exposed to outdoor solar radiation, including reduced electrical performance, shortened lifespan, and the risk of skin burns. In this work, we introduce a novel approach known as the cooling E-textile (CET), which ensures reliable and accurate tracking of uninterrupted physiological signals in intense external conditions while maintaining the device at a consistently cool temperature. Through a co-designed architecture comprising a spectrally selective passive cooling structure and intricate hierarchical sensing construction, the monolithic integrated CET demonstrates superior sensitivity (6.67 x 10(3) kPa(-1)), remarkable stability, and excellent wearable properties, such as flexibility, lightweightness, and thermal comfort, while achieving maximum temperature reduction of 21 degrees C. In contrast to the limitations faced by existing devices that offer low signal quality during overheating, CET presents accurately stable performance output even in rugged external environments. This work presents an innovative method for effective thermal management in next-generation textile electronics tailored for outdoor applications.