Low temperature UV-visible spectra of cytochrome c and microperoxidase-11 are studied experimentally and theoretically using quantum chemical and Poisson-Boltzmann electrostatics models. Spectral splitting in the Q(0,0) visible absorption band is observed at low temperature (<180 K) in all cytochromes c studied. The Q-band is also found to be blue-shifted with decreasing temperature for cytochrome c and microperoxidase-11. Variations in the energy and splitting of the Q-band are interpreted in terms of heme distortions and interactions of the heme charge distribution with the internal electric field of the heme pocket, generated by charged and polar groups in the protein. The temperature dependence of the spectra is interpreted in terms of coupling of the heme electronic transitions to low frequency vibrational modes and thermal expansion/contraction of the protein-solvent lattice.