  We report a precision realization of photonic thermometry using dual-comb
spectroscopy to interrogate a $\pi$-phase-shifted fiber Bragg grating. We
achieve read-out stability of 7.5 mK at 1 s and resolve temperature changes of
similar magnitude--sufficient for most industrial applications. Our dual-comb
approach enables rapid sensing of dynamic temperature, and our scalable and
reconfigurable electro-optic generation scheme enables a broad sensing range
without laser tuning. Reproducibility on the International Temperature Scale of
1990 is tested, and ultimately limited by the frequency reference and
check-thermometer stability. Our demonstration opens the door for a universal
interrogator deployable to multiple photonic devices in parallel. Applications
include on-chip measurements to simultaneously evaluate quantities like
temperature, pressure, humidity, magnetic field and radiation dose.
