Heat flux measurements are very important in the study of the atmospheric boundary layer (ABL) dynamics; heat flux controls ABL stability and is therefore crucial to various topics such as air quality and hydrometeorology. Accurate heat flux measurements can be obtained using the eddy covariance method which requires synchronized, high frequency, wind and temperature measurements. Nevertheless, these measurements require accurate equipment and are often expensive and non-trivial to perform. The present study tries to estimate sensible heat flux for stable and unstable atmospheric conditions through the Monin-Obukhov similarity theory for temperature variance. The studies of fluctuating properties under unstable conditions are abundant and the variance method to estimate sensible heat flux is validated with experimental data for this case. For stable conditions, an empirical method is defined with data collected from a field experiment. The prediction of both atmpospheric conditons are compared to the eddy covariance method.