Three transient phases of droplet heating (cooling) and evaporation are identified. Using characteristic time scales, the dimensionless criteria have been formulated to identify the regimes in which the temperature gradient inside the droplet is significant and should be taken into account. The effect of the internal temperature gradient on droplet evaporation dynamics and the droplet life time has been investigated. This effect is demonstrated in numerical simulations of two distinct liquids (acetone and water) at low (20 °C) and high (1400 °C) ambient temperatures.