This study is the first to contrast two similarity theory methods, the flux variance and the half-order time derivative, over a wide range of atmospheric stability and surface roughness conditions. These two methods were selected because they require only single-level temperature measurement to estimate sensible heat flux. The data used were collected over bare soil, a grass-covered forest clearing, and an even-aged pine forest. For all three sites the flux variance method estimated the sensible heat flux relatively well for unstable atmospheric conditions. The half-order time derivative method was found to be sensitive to the parameterization of the eddy diffusivity, especially for the grass and bare soil field sites. Overall, the flux variance method was able to reproduce the measured sensible heat flux with greater accuracy than the half-order time derivative methods for the three experiment sites.