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VO₂ undergoes a conductivity increase of up to five orders of magnitude as the temperature is increased through 341 K. Recently, the insulator-to-metal transition (IMT) has been triggered with an applied voltage, but debate remains as to whether the transition can be due to electric field effects alone, or whether Joule heating is necessary. Here, we use a conductive AFM tip to locally apply a voltage bias and measure the current through a VO₂ film. By fitting the IV curves immediately preceding the IMT to the temperature-dependent Poole-Frenkel conduction mechanism, we determine the local temperature of VO₂ in the insulating state. We find that the tip has locally warmed the film to 335 K ± 4 K immediately preceding the transition. Therefore, Joule heating plays a significant role in the voltage-triggered IMT in VO₂.