Theoretical evolution of the flare-to-background intensity excess as a function of chromospheric temperature under varying column emission measures (﹩{n}_{\,\rm{e}\,}^{2}L﹩). The four solid curves illustrate the results for different ﹩{n}_{\,\rm{e}\,}^{2}L﹩, ranging from 7 × 10³⁴ cm⁻⁵ to 5 × 10³⁵ cm⁻⁵. The vertical pink dashed line indicates the peak excess, which consistently occurs at ∼4153 K. The vertical purple dashed line marks the physical cut-off temperature at ∼25,000 K. The horizontal gray dashed line represents a flare-to-background intensity excess of 0.2.