Piezoelectric MEMS energy harvesters have demonstrated the ability to be an effective power supply for small devices by collecting energy from readily available ambient vibration and converting it into electrical energy. Such devices can be operated in different environmental conditions where vibration and temperature conditions vary. It is known that when the ambient vibration frequency is slightly away from the resonance frequency of the device, the generated output becomes significantly reduced. It is believed that ambient temperature influences the performance of the energy harvester by changing the materials constants, such as stiffness, piezoelectric constant, etc. However, little research has been focused on the evaluation of the device at different environmental temperatures. In this study, the effect of temperature on the vibration energy harvester was investigated. Bulk scale harvesters from soft and hard PZT were fabricated to investigate the effects of temperature. The output power was characterized to develop a model. A MEMS energy harvester was also systematically examined. Further, the potential to deploy environmental temperature gradients will be discussed.