The effects of ambient temperature on the discharge characteristics of Ne-Xe based micro discharge cells for ac-PDP (plasma display panel) have been studied. In ramp voltage driving, which is generally used as a reset method of PDP, two dissimilar modes of strong and weak discharge were found. As the interval between the former sustaining discharge and ramp voltage discharge becomes greater, the probability of a strong discharge increases. This suggests that a sufficient number of priming particles is necessary for initiating weak mode (Townsend discharge). It was discovered that under higher ambient temperatures, weak discharge occurs more frequently. The discharge time lag observed in square pulse driving of single cells becomes surprisingly smaller under higher ambient temperatures for the constant gas number density condition.