Population fluctuations of peach fruit fly Bacterocera zonata (Diptera: Tephritidae) were monitored in three mango orchards at two locations, viz. Dera Ismail Khan (D.I.Khan) and Paniala for 3 consecutive years, using male sex lure methyl euginol baited traps. Three traps were installed in each orchard and were replenished after every two months. Data on fly catches were recoded at weekly interval at both locations. Weather data on maximum, minimum and mean temperature, percent relative humidity (RH), wind speed, pan evaporation, and mean daily relative humidity were also recorded. Flies population data were correlated with weather variations to figure out the seasonal impact on flies’ activity. The population data at both locations showed two prominent peaks, in late spring and larger one in later summer or early fall. The population build up in the early spring associated with progeny development on ber (Ziziphus jujuba) while first peak was due to fruit fly infestation in guava. The absence of any prominent host fruit between late spring and early summer is the reason of population decline in May, June and July. The second and larger peak was associated with mango, mid and later varieties like Chounsa, Fajri etc. The correlation studies directed a positive and significant relation of population fluctuation with that of maximum, minimum temperature, wind velocity, pan evaporation and mean daily temperature. An inverse and significant relation was observed with percent relative humidity observed at 08:00 am, while weak relation was noted with mean relative and percent relative humidity recorded at 05:00 pm.