Thermal regulation in warm clothing is essential for enhancing human comfort in cold environments. However, traditional warm clothing lacks the ability to adapt to dynamic changes in the human body's microenvironment. Here, we present an adaptive warm cloth, featuring a filling made of a natural bacterial cellulose membrane that responds to human sweating. The cloth's thickness automatically adjusts from 13 millimeters (under low humidity and no sweating conditions) to 2 millimeters (under high humidity and sweating conditions), expanding the thermal regulation capability by 82.8% compared to traditional warm clothing with an unchanged thickness of 13 millimeters. Modeling results further suggest that deploying this adaptive warm clothing across 20 cities in China could extend the duration of the no thermal stress zone by an average of 7.5 hours. Combining exceptional thermal regulation, high stability, and scalability, this clothing represents a notable supplement to existing thermal management technologies.