As wind turbines are likely to be installed in a wide variety of environments, knowledge of their materials mechanical properties under extreme environments is needed. The project presented herein aims at evaluating the effects of temperatures of -40 ℃, 23 ℃, and 60 ℃ on the static properties and fatigue lives of unidirectional glass-epoxy composites as found in wind turbine blades load bearing structures. Tensile and compressive static properties, as well as fatigue lives under R = 0.1 and R = −1 loading are evaluated. Moreover, in an attempt to reduce future tests time by using the highest frequency possible, efforts are spent in evaluating the effects of loading frequency on specimen fatigue lives. Frequencies ranging from 1 Hz to 24 Hz are studied. Results show that even if the static strength of the composite is much improved at low temperature, this does not translate to improved fatigue performances and may actually cause a reduction of fatigue lives. On the other hand, static strength degradation at higher temperatures does equate to a significant reduction in fatigue life. This is particularly true for fully reversed fatigue loading. It is also shown that higher loading frequencies are rapidly deleterious at room and elevated temperatures. However, considering the limited effect of low temperatures on fatigue performances, it is believed that cooling could be coupled to higher frequencies in order to accelerate fatigue testing.