In recent years, accidents of windage yaw discharge occur on transmission lines frequently, and have seriously affected on security and reliability of the power system. Because the prevention measures of windage yaw are expensive and hard to implement and other factors, it is hard to avoid the accident of windage yaw discharge. An online early warning method based on meteorological information for windage yaw discharge of strain tower is proposed from the perspective of operation. This paper aims at the “JG” type strain tower which is common and prone to raise accident of windage yaw discharge. Making use of refined meteorological forecasting information, the windage yaw angle of suspension insulator string is calculated, and then the analytical equation to calculate minimum clearance from center-phase jumper and side-phase jumper to tower body is obtained through leading two dimensional Descartes coordinate system into tower model, and then the comparison with permissible minimum clearance is conducted to get warning results. Moreover, considering that the rain will reduce the discharge voltage of clearance, the influence coefficient of rainfall is introduced to revise the permissible minimum clearance to make the warning more accurate. Finally, the feasibility and accuracy of the proposed method are verified by instance analysis.