As the development of aerospace engineering technology progress more rapidly, now one of the most popular topics is Flapping-Wing Aerial Vehicle. Generally, it has light-weight and small size characteristics, and its small scale is particularly suited for the military mission. On the other hand, the recently extreme weather is becoming worse and worse, thus current work considers the climate and environment effects to measure and calculate how much degradation the environment affects the performance of flapping-wing aircraft. Our research team has studied the impact of weather factors for a long time and collected lots experiences in the analysis of different climatic conditions. In order to realize how much environmental impact does affect, we derive the flight vehicle energy equation to measure its flight performance in terms of a quantitative parameter. To understand the flapping motion physical behavior, the 2-D “figure-eight” flapping airfoil motions are first validated, and then the 3-D butterfly performance parameter under different atmospheric conditions are numerically simulated and compared. Both the butterfly body and wing flapping motions are activated and implemented in current research. Our selection of software is ANSYS FLUENT arranging in pairs with UDF (User-Defined-Function) and DPM (Discrete Phase Model) to fulfill this study. After compared the difference between the weather under no rain condition and heavy rain condition, the code which written in Matlab is taken to calculate its performance. From the difference of performance parameter under clear weather and heavy rain condition, it can show how much flapping frequency it has to be increased to maintain the same flight condition under clear weather. Compared the energy loss between clear weather and heavy rain condition to know how much energy the energy supply device should pay under the heavy rain condition. It is believed that the quantitative information gained in this work will be useful in the later optimal design of flapping wing aerial vehicle under some severe weather situations.