Urban areas influence precipitation, but it remains unclear how these urban effects vary throughout the year. Therefore, this thesis examines monthly urban effects on precipitation variables in the Atlanta region. Precipitation totals, precipitation days, and heavy-precipitation days from 70 precipitation gauges over ten years (2014–2023) were analyzed. Key methods included spatially interpolating precipitation values, assessing correlations between precipitation and upwind imperviousness, and comparing precipitation at downwind gauges with control gauges. Urban effects on precipitation always occurred to downwind (i.e., east/northeast) of Atlanta). Precipitation totals and heavy-precipitation days were enhanced during May, July, and August. Precipitation totals and heavy-precipitation days were suppressed during February and March. Precipitation days were enhanced during most months. Likely mechanisms include the urban heat island effect (UHI) and urban aerosols, with the UHI causing the summer enhancement of precipitation and the aerosols causing both suppression and enhancement of precipitation.