Zirconium alloys are widely used as fuel cladding in light water reactors because of their optimal combination ofmechanical strength, corrosion resistance, and low neutron absorption cross-section. During operation, cladding inevitablyabsorbs hydrogen from the high-temperature coolant. Conventionally, hydride precipitates exhibit a circumferentialorientation under stress-free conditions, and reorientation into a radial morphology is traditionally attributed to sustainedtensile hoop stress. Here, it is demonstrated that pronounced hydride reorientation can occur under stress-free conditions,triggered solely by rapid thermal transients. The experimental results reveal that at a heating rate of 20 ℃/min, a localized,radially oriented hydride aggregation zone—resembling a “sunspot”—emerges on the outer cladding surface. Mechanisticanalysis indicates that rapid heating establishes a steep through-thickness temperature gradient, which, under deformationcompatibility, forces the expanding outer wall to be constrained by the inner wall and consequently drives a dynamiccircumferential tensile stress gradient. This transient gradient drives solute hydrogen toward regions of higher tensile stressvia uphill diffusion and triggers rapid precipitation in the supersaturated matrix, preferentially aligning hydridesperpendicular to the principal tensile axis.