Overhead Transmissions Lines (OTL) are outdoor systems, which can easily be affected by weather fluctuation. In the worst-case scenario, temperature variation, horizontal wind and vertical ice-loading make the value of sag, tension and conductor (cable) length to vary between low to high extremes. The temperature and cable length variations have an effect on the resistance of the OTL. This variation leads to a variable voltage drop, which is mostly considered with load variation. In order to calculate resultant loading, sag, tension, cable length and resistances of an OTL, an uncertainty model based on Standard Affine Arithmetic (SAA) is proposed and the result is compared with the probabilistic Monte Carlo (MC) and Interval Arithmetic (IA) approaches. Based on the test results, the SAA based algorithm gives slightly conservative bound than the IA and MC approaches.