The olive fruit fly Bactrocera oleae (Rossi) (Diptera; Tephritidae) is a relatively recent invasive pest and is considered the primary olive pest in California. Calfifornia’s Central Valley is extremly hot duirng the summer months and the high temperature (heat stress) could dramatically influence the fly’s survival. It is thus critical for the fly to seek out food resource (water and carbohydrate), and refuge during summer. We used a flight mill to quantify the impacts of two diurnal high temperature regimes (65 ºF from 7:00 PM to 12:00 AM and 95 or 100 º F from 12:00 AM through 7:00 PM, the diurnal photophase regime ran from 5:00 AM to 8:00 PM) on the fly’s flight performance. The temperature regimes somewhat reflected the San Joaquin Valley summer conditions and the mid-day rise in temperature. Flight distance and duration of the fly were significantly reduced after pre-flight exposure to two diurnal temperature regimes, when compared to the flies held under constant temperature (75 ºF) prior to test. When no water was provided during the pre-flight temperature treatment, flight distance and duration of the flies were further reduced compared with flies permitted access to water during the exposure. Regardless of the food and temperature conditions, both flight distance and duration of the flies decreased with increasing exposure time to either high temperature regime. Percentage of flies that failed to fly increased with increasing pre-flight heat exposure.