In electronic devices, a high-density electric current applied to the wires causes atoms or vacancies drifts, which is called electromigration. Electromigration produces voids and holes at the cathode side, especially at the wire ends and Via, eventually causing wire failure. The atom and void mass flux due to electromigration is affected by the current density, atom (or void) concentration, stress, and temperature. In this study, we investigated the effects of temperature and heat transfer on void generation, void growth, and microwire failures associated with electromigration. Thermo-reflectance imaging (TRI) was used to simultaneously measure the two-dimensional temperature distributions with the visualization of the voids. The TRI technique was validated by comparing the temperature distribution of an Au microwire heated by Joule heating to numerical computation results. Electromigration measurements were conducted using an Al microwire in which void generation was observed at the cathode end. The growth pattern of the void changed with time, giving different curves for the increasing rate of void size. Furthermore, the local temperature and its gradient significantly affected the void growth. The void growth rate and local temperature exhibited an exponential relationship, highlighting that the diffusivity of the atom (void) plays an important role in local void growth characteristics.