The enhanced heat transfer by oscillating flows past a hot circular cylinder is studied numerically under the conditions of a constant and uniform heat flux on the cylinder surface and a constant temperature at faraway. The stagnant ambient fluid is initially heated by the cylinder to a steady temperature distribution, and is then set forth with a sinusoidal oscillation to cool the cylinder. The velocity field is first computed with a two-dimensional DNS method, and then used to calculate the temperature distribution at the same instant. The transient development of temperature deviation from the initial temperature represents the enhanced cooling due to the oscillating flow. This temperature deviation is presented graphically to demonstrate the existence of two heated regions near the left and right stagnation points on the cylinder against fluid oscillation. The development of the temperature pattern due to the enhanced cooling is found to be highly correlated to the secondary streaming patterns associated with the oscillating flow.