Due to the intermittent and variable nature of wind, grid integration of wind power is a big challenge in power system operation. Studies that evaluate and identify the impact of wind power on power system operation and mitigation techniques is indispensable. This paper has evaluated the hourly variability of hourly wind power production in Ethiopian wind farms. The evaluation has identified the maximum up and down variation of the production. The duration that the hourly step change is greater than 5% and less than -5% to see the duration of calm time also studied. The result show that the extreme maximum up and down hourly wind power production variation is observed in Adama I which is 100% of rated capacity. This is because of the small installed capacity compared to the aggregated production which has the maximum up and down hourly wind power production of 53.40% and -65.7% respectively and this shows that wind power production in Ethiopia is highly ramping up and down. From the simulation result it was clearly observed that the correlation between wind farms is reduced as the distance between them increases. Not only this but also the paper has also shown that the probability of low production is observed during autumn season and probability of high production is observed during spring and winter season.This challenge increases if the penetration level of wind increases. Thus, the authors recommend that before grid integration of wind power, it is necessary to evaluate its impact on grid operation.