The infrared absorption and Raman spectra of polycrystalline tetrachlorocuprate(II) dihydrates M2CuCl4.2H2O (M = K, Rb, Cs, NH4) contain minima in the OH stretching region which sharpen at low temperature. These minima are shown to be 'Evans holes', or negative absorption features, caused by Fermi resonance between the broad and intense H2O stretching fundamental V1 and a relatively narrow band due to the overtone of the H2O bending vibration 2V2. Our findings confirm that Fermi resonance can lead to unusual spectral features, which must be taken into account in the analysis of the stretching region of the spectra of H2O and D2O in condensed phases, as has been done by Scherer etal. for the spectrum of liquid water.