Field test data obtained from 2*100 W mono-crystalline photovoltaic solar modules installed on the rooftop of WASCAL’s building on a tilted surface of 15º facing south and ambient temperature measured around the modules were analyzed in detail. In addition to these field test data, the inclined global solar radiation measured in CNES and the relative humidity data obtained from NASA power website were also used. Then the impact of solar irradiation, ambient temperature, dust accumulation, cloud cover, and relative humidity on the performance of the mono-crystalline solar module had been investigated under Niamey’s environment. The results obtained show that the impacts of ambient temperature and dust accumulation are more crucial for the study area. For the ambient temperature, the correlation coefficient is estimated to -0.53 for both May and June and -0.28 and -0.20 for July and August respectively. The slope between the conversion efficiency and the ambient temperature is estimated to -0.49%/ºC compare to -0.45%/ºC provided by the manufacturer under STC. This result indicates that it is very important to consider the temperature characteristics in developing solar cell. For the dust accumulation, results show that the average daily efficiency drop in June due to dust accumulation is estimated to 0.18%/day corresponding to an overall efficiency drop of 5.8%/month. This limitation makes solar PV unreliable for remote devices and thus strongly suggests the challenge of cleaning the module. However in July the effect is insignificant due to less amount of dust in this month and regular precipitation that washes the module. For the relative humidity and cloud cover, the impacts are only noticeable in July and August.