Despite reductions in automobile and industrial emissions, Houston continues to be designated as a non-attainment area for ozone (O3) by the Environmental Protection Agency (EPA). Upper-level synoptic maps and vertical atmospheric temperature structures associated with Houston's ozone episodes were analyzed in order to assist with better air quality forecasts in the future. This study focuses on ozone episodes where the peak 8 hour average exceeded 85 ppb which occurred in August and September 2006 during the Texas Air Quality Study-II (TexAQS-II). Synoptic composite maps of geopotential height show that a close proximity of an upper-level ridge can increase the probability that Houston will experience elevated ozone levels. Also, rawinsonde soundings were launched twice daily at 0700 and 1900 central daylight time (CDT), with 4 additional soundings on intensive operations days. These soundings revealed a contrast between the episode days of August and those of September. It is demonstrated that most ozone episodes occurred in a post-frontal environment. The northerly or northeasterly winds behind a cold front helped to increase background ozone levels which contribute to an increase in Houston's average 8 hour ozone peak. Analyses of inversions present in the soundings revealed that the strength of the morning radiation inversion is not a major factor in Houston's ozone concentration. However, September episode days usually exhibited an elevated inversion. This inversion may not have a direct effect on Houston's ozone concentration; however it could be a sounding feature which could assist air quality forecasters in the future.