Maricopa County has exceeded the 24 hour National Ambient Air Quality Standard (NAAQS) for Particulate Matter 10 micrometers in diameter or smaller (PM-10) of 150 micrograms per meter cubed (μg/m3) since 1990. Construction and construction related activities have been recognized as the highest contributors to high PM-10 levels. An analysis of days exceeding 150 μg/m3 for four of Maricopa County‟s monitors that most frequently exceed this level during the years 2007, 2008, and 2009 has been performed. Noted contributors to PM-10 levels have been identified in the study, including earthmoving permits, stationary source permits, vacant lots, and agriculture on two mile radius maps around each monitor. PM-10 levels and wind speeds for each date exceeding 225 μg/m3 were reviewed to find specific weather or anthropogenic sources for the high PM-10 levels. Weather patterns for days where multiple monitors exceed 150 μg/m3 were reviewed to find correlations between daily weather and high PM-10 levels. It was found that areas with more earthmoving permits had fewer days exceeding 150 μg/m3 than areas with more stationary permits, vacant lots, or agriculture. The Higley and Buckeye monitors showed increases in PM-10 levels when winds came from areas covered by agricultural land. West 43rd Avenue and Durango monitors saw PM-10 rise when the winds came in over large stationary sources, like aggregate plants. A correlation between weather events and PM-10 exceedances was also found on multiple monitors for dates both in 2007, and 2009.