The association between a developing urban heat island and local monthly averaged wind speeds is examined in this investigation. Results from a series of statistical analyses show a significant increase in wind speeds in Phoenix, Arizona during the period of rapid heat island development. The increase in winds is found to be much stronger at 0500 MST than at 1400 MST. Increased instability and the development of a strong heat low circulation in the urban environment are suggested as probable causes for the increased wind speeds.